Put the pan on medium/high heat and let it heat up.
Chop up the onion and mushrooms.
Crack open the eggs into the bowl.
Using a whisk or a fork, whisk the eggs together like you’re making scrambled eggs or an omelet.
Add the splash of milk or whipping cream and continue whisking to make the eggs light and fluffy.
Add the spices and cheese and set aside.
The pan should be hot enough to cook the onion. Drop the heat to medium. Add the butter and let it melt. After it’s melted add the onion. Cook the onion for about a minute then add the mushrooms for about 2 minutes.
Add the egg mixture on top of the onions and mushrooms and let it spread out over the entire bottom of the pan. Let it cook for about 2-3 minutes. Put the tortilla shell on top of the egg mixture. Using your hand slightly push down on it so it sticks to the eggs.* Cook until the egg is no longer jiggly, around 5 minutes.
When done cooking, loosen the egg and tortilla shell from all sides. When you're moving the pan back and forth the egg mixture and tortilla should move freely. Next part is a little tricky. Bring a cutting board on top of the pan. Flip the pan so the cooked egg and tortilla fall on top of the cutting board. You may need to use your hand to support the tortilla. Do all this in one swift motion.
The tortilla shell should be on the bottom and the egg mixture on top.
Spread the mayo (or any kind of sauce you like) all over the eggs.
Roll the tortilla into a burrito and cut in the middle.