Form the ground beef into two separate patties and season with salt and pepper to taste. Saute over medium high heat until cooked to your liking. Remove and keep warm. 

Add the oil to the same skillet and saute the onions until softened. 

Cook the bacon until crispy and set aside. 

Mix together the eggs, milk, heavy whipping cream, garlic powder, 1 tsp salt and 1 tsp pepper in a bowl until well combined. 

Dip the slices of bread in the egg mixture and then toast in a large skillet over medium heat until crispy on both sides. 

Layer some big mac sauce on the inside of the slices of toast if desired. 

Place a burger patty on two slices of bread, and top with a slice of American cheese, some sauteed onions and 2 slices of bacon. 

Place another piece of toast on top of each sandwich and serve.