In a small bowl, beat eggs, salt and pepper. Coat a 10-in. skillet with cooking spray and place over medium heat. Add egg mixture. As the eggs set, lift edges, letting uncooked portion flow underneath.
When eggs are nearly set, place cheese, salsa and, if desired, chiles and mushrooms over half of eggs; fold in half. Cover and let stand until cheese is melted, 1-2 minutes. If desired, serve with additional salsa and sour cream.