Preheat your oven to 350°F (175°C).

In a large skillet over medium-high heat, cook the ground beef until browned, about 5 minutes. Add the diced onions, Worcestershire sauce, garlic powder, salt, and pepper. Cook for an additional 5 minutes.

Drain excess grease and return the beef and onions to the skillet.

Add cream cheese into the skillet and stir until melted, about 2-3 minutes.

Remove from heat and stir in the dill pickle relish.

Grease an 11x7-inch baking dish and spread the beef mixture evenly.

In a mixing bowl, whisk together the eggs, heavy cream, and remaining salt and pepper until smooth.

Pour the egg mixture over the beef layer and shake to distribute evenly.

Sprinkle shredded cheddar cheese over the top.

Bake for about 30 minutes until the edges are bubbling and the center is set.

While baking, mix mayonnaise, yellow mustard, white wine vinegar, paprika, onion powder, and garlic powder to make the Big Mac sauce.

Let the casserole sit for about 15 minutes before serving. Drizzle the sauce over each serving.