1. Patties part one: Melt 2 tablespoons butter in a small bowl and stir in 1 tablespoon Worcestershire sauce and 1 teaspoon smoked paprika. Pour the butter mixture over the ground beef and use your hands to mix until just combined, don’t overmix it. Shape the  mixture into four balls, put them on a plate and pop it in the fridge to chill while you prep the other components.
2. Onions: Preheat flat top grill or large sauté pan over medium low heat. Melt 1 tablespoon butter and 1 tablespoon oil on the grill or in the pan. Add the sliced onions, tossing to get them evenly coated in fat. Cook over medium low, stirring occasionally for ten minutes until softened and starting to develop some color.
3. Sprinkle on 2 teaspoons brown sugar, 1 tablespoon balsamic vinegar and a pinch of salt over the onions, tossing to combine. Continue cooking for 10-15 minutes, stirring every minute or so. Be careful to watch the heat, it’s best to go low and slow so the onions don’t burn. When the onions are deeply golden brown, caramelized and jammy, remove to a bowl.
4. Patties part two: Increase grill heat to medium-high. Plop each ball onto the flat top and sprinkle with kosher salt. Place a small square of parchment paper on the patty and use a cast-iron grill press to smash the patty in one quick, aggressive motion. Really smash that bad boy, you’re going for a super thin patty. Repeat with the remaining patties. Cook for 2-3 minutes, until the burgers have craggly, browned edges. Flip and top with a slice of cheese, cooking for another 1-2 minutes. Remove to a plate, you’re ready for assembly!
5. Assembly: Whisk together all of the ingredients for the special sauce. Taste and season with a pinch of salt or dash of sriracha, per your taste. Toast up the brioche buns (I like to butter them and bake at 400 degrees for 5 minutes). Layer -> bottom bun, huge spoonful of sauce, caramelized onions, beef patty, tomato, pickles, lettuce, huge spoonful of sauce, top bun.

WOWWWWW. Invite me over, I want one.