Preheat the oven to 350 degrees F.
If making one: Cook the bacon in a skillet over medium-high heat until browned but still flexible.
If making more than one: Lay out bacon on a foil and parchment-lined cookie sheet. Bake in the 350 degree F oven for 10 to 12 minutes. (You want the bacon to be cooked and flexible; not crispy.) Or cook in a skillet over medium-high heat until browned but still flexible.
Set up ramekins (4-ounce) or you can use a muffin tin. But if you are using the ramekins, place them on a cookie sheet. If you are using the muffin tin, put a little water in the unused muffin cups; this saves the cups from burning.
When bacon is done, wrap a slice around the inside of the ramekin or muffin cup.
Place a teaspoon of melted butter (or bacon grease) in the bottom of the ramekin or muffin cup.
Drop in the egg.
Bake in the preheated oven.
After about 10 to 15 minutes, place a 1/4 slice of cheese over the egg, and continue to bake until egg is cooked and the cheese is melted.