Place the onion, garlic, jalapeño into a mini food processor, then blitz to chop. Add the eggs, Worcestershire sauce, Dijon, BBQ sauce & horseradish, then blitz to combine. (Alternatively: mince onion, garlic, and jalapeño finely and mix ingredients in a large bowl.)
Add mixture to a large bowl, then add panko and stir to combine.
Add Ontario Beef to the bowl and mix until all ingredients are combined.
Shape into 6 x 6 ¼-6 ½ oz patties (about ¾” thick x 4 ½” diameter). Using your thumb, press the middle of each patty a few times to create an indent that will keep the burgers from puffing up when cooked. Before grilling, place the patties on a tray lined with wax paper in the freezer for 30 minutes (cold burgers cook better).
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, the brush the top while on the grill. Close lid and grill, turning occasionally and flipping about 4 minutes into the cook. Total cook time 8 – 10 minutes. (Internal temperature 155°F - 160°F). Let patties rest 5 minutes, tented in foil, before topping.
Toast the brioche burger buns and build the burgers. Shmear mustard on the bottom bun, add the lettuce, tomatoes, the cheese burger patty, pickles, marinated onions, and finally the beef bacon.
Serve and enjoy!