Instead of heading to McDonald's, make a better version of the Egg McMuffin at home. A mason jar lid will help you perfect the cooked egg for this iconic breakfast sandwich (or any egg sandwich, for that matter).
Photo by J. Kenji López-Alt.
Serious Eats' J. Kenji López-Alt shares this egg cooking technique and explains why you want to use the entire mason jar lid -- not just the ring mould but the cover as well:
I tried placing a ring mould directly into my skillet, using it to help the eggs keep their shape as they cooked -- this is similar to how McDonald's does it in-store -- but it was difficult to get them to cook evenly without browning. McMuffin eggs should be tender and white on both sides. I also tried microwaving eggs in ramekins, both with and without additional water. This was moderately successful, but it was difficult to nail the right consistency.
[...] By placing the lid and screw ring of a Mason jar upside down in a skillet, I had a perfect English muffin -- sized mould in which to cook my egg. Moreover, because the egg never comes into direct contact with the bottom of the pan, it stays tender and white as it cooks.
Add some water to the skillet and cover it all up with a lid to help keep the eggs tender and moist. In two minutes, you have a perfectly cooked egg for your improved McMuffin clone.
Check out Kenji's article below for the complete step-by-step directions to better homemade Egg McMuffins.
The Food Lab: Building a Better Egg McMuffin [Serious Eats]