Preheat a skillet or grill pan over medium-high heat until hot

Season ground beef with salt and pepper, then divide into 4 equal patties

Lightly spread mustard on one side of each patty for added flavor

Cook patties for 4–5 minutes per side until browned and cooked through

Add cheese slices during the last minute to melt

In a bowl, mix mayonnaise, ketchup, relish, and vinegar to create the sauce

Wash and dry lettuce leaves, keeping them whole for wrapping

Lay lettuce leaves flat and spread a small amount of sauce

Place cooked patties on top, followed by tomatoes, onions, and pickles

Add extra sauce if desired and top with another lettuce layer

Gently fold or wrap and serve immediately