Step 1

On a small sheet tray or large plate, loosely spread minced bacon in a single layer, then top with ground beef in a single layer. Using a bench scraper, cut meat mixture down the middle and stack one-half of mixture on top of the other. Repeat cutting and stacking twice more, lightly patting down to combine mixture.

Step 2

Divide mixture into six equal portions, 4 ounces each. Gently toss each portion back and forth between your hands to shape them into balls, then lightly flatten each ball into a 3 ½”-wide patty.

Step 3

In a large skillet over medium-high heat, heat oil. Add patties and cook, in batches if necessary, until a thick golden crust has formed, 3 to 4 minutes. Season tops of patties lightly with salt, then flip and cook on other side until patties reach an internal temperature of 145°, about 3 minutes more. Transfer to a plate and let rest 3 minutes.

Step 4

Meanwhile, make special sauce: In a medium bowl, stir together all sauce ingredients.

Step 5

To serve, place each patty inside a lettuce leaf folded in half. Top with a heaping tablespoon of special sauce and sliced onions.