Place the onion, garlic, salt, pepper, and Dijon into a mini food processor, then blitz to chop. Add the egg, then blitz again to combine. (Alternatively: mince onion and garlic and mix ingredients in a large bowl.)
Add mixture to a large bowl, then add panko and stir to combine.
Add turkey to the bowl and mix until all ingredients are combined.
Portion the turkey mixture into 6 x 6 ⅛-6 ¼ oz balls, then add ½ oz of stilton cheese to each ball.
Fold the turkey around the cheese and shape each ball into a patty, approximately ¾” thick x 4 ½” diameter.
Before grilling, place the patties on a tray lined with wax paper and place in the freezer for 30-60 minutes (cold burgers, crisp up better on the exterior and it should keep the cheese from premature oozing).
Preheat grill to medium-high heat (400°F - 450°F).
Brush each patty with olive oil and place oil side down on the hot grill, then brush the top with a little oil while on the grill. Close lid and grill, turning once and flipping about 6 minutes into the cook. Grill for 2 minutes, then add a spoonful of the Spicy Grape Jam and spread out over the top of the burger.
Cook for another 4 – 6 minutes until the internal temperature of the meat is 160°F (total cook time 12-14 minutes). Let patties rest 5 minutes, tented in foil, before topping and serving.
Garnish with sauteed onions, pickled jalapeños, dill pickles and bib lettuce. Serve with more spicy grape jam and your favourite condiments.
(Make-ahead: Layer between waxed paper in airtight container and refrigerate for up to 24 hours or freeze and cook later from frozen)