How to Cook Everything: The Basics: All You Need to Make Great Food--With 1,000 Photos: A Beginner Cookbook

by Mark Bittman

Cooked and chopped mushrooms, onion, spinach, or simply cooked leftover vegetables, ½ to 1 cup

9/23/23 - Added some mushrooms and spinach to my daily omelet. Can never go back to just egg and cheese now. (I used to spend $20 a pop on omelets as a weekly treat from IHOP. Now I can make them fresh daily for a tenth of the price!)