Gather all ingredients and ensure wagyu ground beef is at room temperature.

Slice brioche buns, tomatoes, and onions; wash lettuce leaves.

In a bowl, gently combine wagyu beef with salt and pepper.

Divide beef into four portions and shape into ¾-inch-thick patties.

Preheat grill or skillet over medium-high heat and add olive oil.

Cook patties for 4 minutes on one side, then flip and cook for 3-4 more minutes.

Place a slice of cheddar cheese on each patty during the last minute of cooking.

Toast brioche buns on the grill or skillet for 1-2 minutes until golden.

Spread mayonnaise and ketchup on the bottom half of each bun.

Layer buns with lettuce, tomato slices, onions, and cooked patties, then top with bun.