Have your vegetables set out. Go ahead and slice your mushroom, green onions, and have your potatoes ready. If you don't have potatoes, omit them, or if you need to make some you can find my easy potato hash recipe here.
Crack your eggs in a bowl.
Mix them with a whisk or fork until the egg whites and yolks are completely blended together.
Heat your skillet on low heat, and let the butter melt.
Once the butter is melted add your eggs and let them set until the bottom is no longer clear and the edges start to cook, the middle should still have plenty of uncooked eggs. Think like a pancake, the edges are somewhat done, but the middle is still full of uncooked batter.
Add your cheese, potatoes, and mushrooms on one side, and spinach on the other.
Fold the omelette in half before it cooks too much more or it won't stay closed. Unfortunately mine is stuck, so the edges are a tad rough.
Let each side cook until each side has a golden brown color to it.
Plate and add the green onions to it. Enjoy!