Super easy, you can change it up to make lots of different muffins.
Full disclosure: I didn't come up with this, but I also don't remember where I saw it. I'm sure I altered it a bit as well. Oh well.
Blanch, or half-fry some bacon. One slice per egg you plan to make. Fry an extra slice or two all the way done if you plan on adding bacon bits to the eggs as I did.
I had mushrooms in the fridge so I sliced two up and fried the slices in the bacon grease while the last two slices were cooking. About 15-20 each side.
Using a couple of forks, drop the bacon in a cup of a muffin pan, pressing the bacon so it lines the cup as best you can. It helps in removal if the pan is non-stick, but the bacon grease dripping in the cup helps.
Crack an egg into each bacon lined cup.
Place one of the fried mushroom slices on top of the egg-cup.
Sprinkle salt, pepper, basil and crumbled bacon bits to the top of each egg-cup.
Cover each egg-cup with cheese. I had only American slices, which were fine, but a nice cheddar would have been great.
Sprinkle Parmesian cheese on each egg-cup.
Bake for 15 minutes at 350. The yellow should be just starting to cook at this point. Adjust times up or down depending on how you like your eggs.
If the eggs are cooked enough, they should come out of the muffin pan cups with a little coaxing. I slid a butter knife around the edges of each one and used a fork (or spoon) to finish the job. They then slid easily onto the plate, looking like little egg muffins.