This velvety cauliflower leek soup hits you first with the crunch of golden sourdough laced with toasted cheddar before giving way to rich, caramelized cauliflower and sweet, buttery leeks. Aged white cheddar weaves through every spoonful to add deep, savoury warmth, while a touch of Dijon brightens the finish.
When soup season arrives, taking a few extra minutes to roast your ingredients changes everything. We start by roasting the florets until the edges turn golden and nutty. Slow-sweating leeks in butter provides a sweet, aromatic base, while Yukon Gold potatoes lend a naturally silky texture once puréed. Finished with sharp white cheddar and topped with freshly baked cheddar sourdough croutons, this dish delivers restaurant-quality warmth straight from your kitchen.
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Why We Love This Recipe
- Deep Flavour Development: Roasting the cauliflower until caramelized gives the base a rich, nutty flavour that plain boiled cauliflower cannot match.
- Silky, Grain-Free Texture: Blending starchy Yukon Gold potatoes with slow-sweated leeks creates a velvety body without relying on heavy thickeners.
- Textural Contrast: Crispy sourdough croutons baked with melted, lacy aged cheddar add a satisfying crunch to every spoonful.
- Balanced Acidity: A touch of Dijon mustard and fresh lemon juice brightens the rich cheddar and heavy cream.
What is a Leek Sweat?
Sweating leeks means cooking thinly sliced leeks gently in fat over low to medium-low heat with a pinch of salt. Unlike sautéing or searing, the goal is to soften the vegetable and release its natural sugars without letting it brown, creating a sweet, tender foundation for soups and sauces.
Ingredients
Roasted Cauliflower
- Cauliflower florets
- Extra virgin olive oil
- Kosher salt
- Black pepper
Soup Base
- Unsalted butter
- Leeks
- Garlic
- Yukon Gold potato
- Low-sodium vegetable or chicken stock
- Dijon mustard
- 35% heavy cream
- Aged white cheddar
- Lemon juice
- Kosher salt
- Black pepper
Cheddar Sourdough Croutons
- Sourdough bread
- Extra virgin olive oil
- Kosher salt
- Aged white cheddar
To Finish
- Fresh chives
- Black pepper
See the recipe card below for quantities.
Instructions
Roast the Cauliflower
Preheat your oven to 425°F (220°C) conventional bake with racks positioned in the upper and lower thirds.
Separate your cauliflower florets, reserving any very small pieces or tiny crumbles so they do not burn on the sheet pans. Set those small raw pieces aside.
Toss the larger cauliflower florets with 3 tablespoon extra virgin olive oil, ¾ teaspoon Windsor Kosher salt, and ⅜ teaspoon black pepper.
Divide between two large sheet pans, spreading the florets into a single layer with space between them.
➡️Note: If your oven cannot accommodate two pans with adequate airflow, roast in two separate batches.
Roast for 25 to 30 minutes, rotating the pans between racks and flipping the cauliflower after 18 minutes. The cauliflower should be tender with golden-brown, caramelized edges. Do not roast until dry.
Sweat the Leeks
While the cauliflower roasts, melt 3 tablespoon unsalted butter in a 5 to 6-quart stock pot over medium-low heat.
Add the sliced leeks and a small pinch of salt. Cook for 9 to 12 minutes, stirring occasionally, until very soft and sweet, but not browned.
Add the chopped garlic and cook for 30 to 45 seconds until fragrant.
Cook the Potatoes & Reserved Raw Cauliflower
Add the diced Yukon Gold potato, the reserved small raw cauliflower pieces, and 5¼ cups stock to the Dutch oven.
Bring to a boil over medium-high heat, then immediately reduce to a gentle simmer.
Partially cover and simmer for 10 to 12 minutes, or until both the potatoes and small cauliflower pieces are completely tender when pierced with a knife.
Stir in all of the roasted cauliflower from the oven. Return to a gentle simmer for 5 minutes to allow the caramelized, roasted flavours to integrate into the broth.
Purée until Silky
Remove the pot from the heat.
For the smoothest texture, purée the soup in small batches in a high-powered countertop blender, keeping the lid’s centre cap slightly vented to release steam. Alternatively, use an immersion blender directly in the pot until completely smooth.
➡️Blender Safety: Avoid overfilling the blender jar with hot soup. Work in small batches and hold a folded towel over the lid cap to let steam escape safely.
Return the puréed soup to the cleaned pot over low heat.
Incorporate Cream, Dijon, and Cheddar
Stir in 1½ teaspoon Dijon mustard and ¾ cup heavy cream. Heat gently until hot and steaming; do not bring the soup to a boil.
Remove the pot from the heat source.
Gradually add the 6 oz grated aged cheddar, one small handful at a time, stirring constantly until fully melted before adding the next.
Stir in ¾ teaspoon fresh lemon juice. Taste the soup before adding more salt, since the cheese and stock add sodium. Season with freshly ground black pepper to taste.
Adjust Consistency
Check the thickness. The soup should coat the back of a spoon smoothly.
If the soup is too thick, stir in additional warm stock, ¼ cup (60 mL) at a time, until the desired viscosity is reached.
Keep warm over very low heat without boiling.
Bake the Cheddar Sourdough Croutons
Reduce the oven temperature to 375°F (190°C).
Toss the sourdough cubes with 1½ tablespoon olive oil and ⅜ teaspoon salt. Spread in a single layer on a baking sheet.
Bake for 7 to 9 minutes, tossing once, until beginning to crisp.
Remove the pan, scatter the 2¼ oz grated cheddar over the croutons, and return to the oven for 3 to 5 minutes until the cheese is melted and crispy around the edges.
Cool for 5 minutes to allow the cheddar crust to harden.
Serve
Ladle the hot soup into warmed bowls. Top each serving with 5 to 7 cheddar sourdough croutons, fresh chives, and freshly cracked black pepper.
Tips, Substitutions & Serving Suggestions
Crucial Technique Tip
- Avoid Grainy Cheese Soup: Pre-shredded packaged cheeses contain anti-caking cellulose that prevents smooth melting. Grate block cheddar by hand. Always remove the pot from direct heat before stirring in the cheddar, as boiling cheese causes fats and solids to separate.
Substitutions
- Cauliflower Leek Soup Vegan / Dairy-Free Option: Substitute unsalted butter with olive oil, heavy cream with full-fat coconut milk or cashew cream and use a high-quality plant-based sharp cheddar alternative.
- Stock Selection: Use low-sodium vegetable stock for a vegetarian meal, or low-sodium chicken stock for a deeper savoury note.
Serving Suggestions
- Pair this soup with a Simple Green Salad with Shallot Vinaigrette to cut through the richness of the cheddar and cream.
- For added protein, top with crispy bacon bits alongside the sourdough croutons.
Transparency is important to us! We are Hestan Culinary ambassadors, and this post contains affiliate links. The thoughts, tips, and results shared in this recipe are 100% our own!
We prepared these Cauliflower Leek Soup using the new Hestan Culinary CopperBond® Aura™ 6-qt Stock pot along with a ¼ Sheetpan and chef's tools.
CopperBond Aura is a special limited-production collection, handcrafted in Italy with a professional-grade 1.5 mm pure copper exterior bonded directly to a durable, nonreactive satin stainless steel interior. The copper responds quickly to temperature adjustments, offering the control needed to achieve a deep sear, a gentle braise and a smooth, cohesive sauce.
Love this Cauliflower Leek Soup? Try these Cauliflower Recipes Next:
- Our viral Golden Cauliflower Steaks with Whipped Sweet Potatoes
- Creamy Cauliflower with Spinach Pasta Bake
- Roasted Delicata Squash & Cauliflower
- Buffalo Cauliflower Mac and Cheese
📖 Recipe
Roasted Cauliflower Leek Soup with Cheddar
Ingredients
➡️Note on Scaling the Recipe: When scaling to 2X or 3X, the light grey ingredient notes and the instructions remain unchanged. Please adjust as needed.
Roasted Cauliflower
- 2¼ lb cauliflower florets 1.02 kg
- 3 tablespoon extra virgin olive oil 45 mL
- ¾ teaspoon Windsor Kosher salt
- ⅜ teaspoon freshly ground black pepper
Soup Base
- 3 tablespoon unsalted butter 42 g
- 3 medium leeks white and pale green parts only, thinly sliced and thoroughly washed (about 3 cups / 330 g)
- 3 garlic cloves finely chopped
- 7½ oz Yukon Gold potato 210 g, peeled and cut into ½-inch pieces
- 5¼ cups low-sodium vegetable or chicken stock 1.25 L , plus more as needed
- 1½ teaspoon Dijon mustard
- ¾ cup 35% heavy cream 180 mL
- 6 oz aged white cheddar 170 g, finely grated by hand
- ¾ teaspoon fresh lemon juice plus more as needed
- Windsor Kosher salt to taste
- Freshly ground black pepper to taste
Cheddar Sourdough Croutons
- 4½ oz sourdough bread 128 g, cut into ½ to ¾-inch cubes (about 3 cups)
- 1½ tablespoon extra virgin olive oil 22½ mL
- ⅜ teaspoon Windsor Kosher salt
- 2¼ oz aged white cheddar 60 g , finely grated by hand
To Finish
- 3 tablespoon finely sliced fresh chives
- Freshly ground black pepper
Instructions
Roast the Cauliflower
- Preheat your oven to 425°F (220°C) conventional bake with racks positioned in the upper and lower thirds.
- Separate your cauliflower florets, reserving any very small pieces or tiny crumbles so they do not burn on the sheet pans. Set those small raw pieces aside.
- Toss the larger cauliflower florets with 3 tablespoon extra virgin olive oil, ¾ teaspoon Windsor Kosher salt, and ⅜ teaspoon black pepper.
- Divide between two large sheet pans, spreading the florets into a single layer with space between them.
- Roast for 25 to 30 minutes, rotating the pans between racks and flipping the cauliflower after 18 minutes. The cauliflower should be tender with golden-brown, caramelized edges. Do not roast until dry.
Sweat the Leeks
- While the cauliflower roasts, melt 3 tablespoon unsalted butter in a 5 to 6-quart stock pot over medium-low heat.
- Add the sliced leeks and a small pinch of salt. Cook for 9 to 12 minutes, stirring occasionally, until very soft and sweet, but not browned.
- Add the chopped garlic and cook for 30 to 45 seconds until fragrant.
Cook the Potatoes & Reserved Raw Cauliflower
- Add the diced Yukon Gold potato, the reserved small raw cauliflower pieces, and 5¼ cups stock to the Dutch oven.
- Bring to a boil over medium-high heat, then immediately reduce to a gentle simmer.
- Partially cover and simmer for 10 to 12 minutes, or until both the potatoes and small cauliflower pieces are completely tender when pierced with a knife.
- Stir in all of the roasted cauliflower from the oven. Return to a gentle simmer for 5 minutes to allow the caramelized, roasted flavours to integrate into the broth.
Purée until Silky
- Remove the pot from the heat.
- For the smoothest texture, purée the soup in small batches in a high-powered countertop blender, keeping the lid's centre cap slightly vented to release steam. Alternatively, use an immersion blender directly in the pot until completely smooth.
- Return the puréed soup to the cleaned pot over low heat.
Incorporate Cream, Dijon, and Cheddar
- Stir in 1½ teaspoon Dijon mustard and ¾ cup heavy cream. Heat gently until hot and steaming; do not bring the soup to a boil.
- Remove the pot from the heat source.
- Gradually add the 6 oz grated aged cheddar, one small handful at a time, stirring constantly until fully melted before adding the next.
- Stir in ¾ teaspoon fresh lemon juice. Taste the soup before adding more salt, since the cheese and stock add sodium. Season with freshly ground black pepper to taste.
Adjust Consistency
- Check the thickness. The soup should coat the back of a spoon smoothly.
- If the soup is too thick, stir in additional warm stock, ¼ cup (60 mL) at a time, until the desired viscosity is reached.
- Keep warm over very low heat without boiling.
Bake the Cheddar Sourdough Croutons
- Reduce the oven temperature to 375°F (190°C).
- Toss the sourdough cubes with 1½ tablespoon olive oil and ⅜ teaspoon salt. Spread in a single layer on a baking sheet.
- Bake for 7 to 9 minutes, tossing once, until beginning to crisp.
- Remove the pan, scatter the 2¼ oz grated cheddar over the croutons, and return to the oven for 3 to 5 minutes until the cheese is melted and crispy around the edges.
- Cool for 5 minutes to allow the cheddar crust to harden.
Serve
- Ladle the hot soup into warmed bowls.
- Top each serving with 5 to 7 cheddar sourdough croutons, fresh chives, and freshly cracked black pepper.
💬Tried this Recipe?
- We'd really appreciate a rating and a quick review! It helps more home cooks find the recipe, and we love hearing what you think.
Notes
Crucial Technique Tip
- Avoid Grainy Cheese Soup: Pre-shredded packaged cheeses contain anti-caking cellulose that prevents smooth melting. Grate block cheddar by hand. Always remove the pot from direct heat before stirring in the cheddar, as boiling cheese causes fats and solids to separate.
Substitutions
- Cauliflower Leek Soup Vegan / Dairy-Free Option: Substitute unsalted butter with olive oil, heavy cream with full-fat coconut milk or cashew cream and use a high-quality plant-based sharp cheddar alternative.
- Stock Selection: Use low-sodium vegetable stock for a vegetarian meal, or low-sodium chicken stock for a deeper savoury note.
Serving Suggestions
- Pair this soup with a Simple Green Salad with Shallot Vinaigrette to cut through the richness of the cheddar and cream.
- For added protein, top with crispy bacon bits alongside the sourdough croutons.
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