Step 1

In a large bowl, add all of the ground beef. Use a large spoon to break it up, and then mix in the eggs. Mix until the eggs are fully incorporated to bring the ground beef mixture together.

Step 2

Set up a workstation with parchment paper. Divide the ground beef into four equal portions. Roll each section into a ball, flatten into a patty, and then place onto the parchment paper. Create a well in the middle of each patty, divide the cheese, and then press it into the middle of the patty. Work the meat to cover the cheese. Place the patties in the fridge to cool and rest for 30 minutes.

Step 3

While the patties are resting, slice the onion and tomato into thick slices. Mix the mayonnaise and Dijon mustard together in a small bowl and set aside.

Step 4

Turn your grill on high. Remove the patties from the fridge to allow them to come up to room temperature just before grilling. Make sure the grill is very hot before adding your patties. Drizzle olive oil over each patty, and sprinkle with salt and pepper. Roll the sides of the patties to fully season every part of the meat.

Step 5

Place the patties on the hot grill and close the lid to allow them to begin cooking. Allow to cook for about four minutes before flipping.

Step 6

While the burgers are cooking, season the thickly sliced onions with oil, salt, and pepper, and put them on the grill. Allow them to cook. Prepare the buns by seasoning them with oil, salt, and pepper, and toast both sides of each bun on the grill.

Step 7

Once the buns are toasted, remove them from the grill and get the burger setup ready. Add a spoonful of the mayo-mustard mixture to the top and bottom of each bun. Add a piece of lettuce on top, and then top with a tomato slice. Sprinkle salt and pepper on top of the tomato slice, and then add another small spoonful of the mayo-mustard mixture.

Step 8

Just before your burgers are ready to come off of the grill, baste each patty with butter. Baste each side for great added flavor.

Step 9

Once the patties are finished cooking and basted with butter, remove them from the grill and place a patty directly on each burger set-up. Top with a few slices of grilled onion, and then place the top bun on top to finish the burger. Serve immediately.