Take 4 slices of bread and cut a 3 inch hole in the center. Remove the inner bread and butter both sides. For the other 4 slices, only butter one half.
Heat skillet or griddle to medium heat. Place one bread slice with hole and one full bread slice butter side down in the pan. Put a slice of cheddar cheese on the full bread slice and top with burger, fried onions & 2 slices of bacon.
Crack an egg into the hole in the other slice of bread. Season with salt & pepper, if desired. Cook 2 minutes and flip egg piece. Cook another minute or 2 until yolk is done to your liking. Top burger with this slice.
Place on a plate and cut in half diagonally. Serve immediately.