In a small bowl, combine the avocado, sour cream, chilies, onion, lemon juice, salt if desired, pepper and hot pepper sauce; set aside.
In a 10-in. nonstick skillet, melt butter over medium-high heat. Add tortilla pieces; cook for 2 minutes or until softened. Meanwhile, whisk eggs. Add eggs to skillet (mixture should set immediately at edges).
As eggs set, push cooked edges toward the center, letting uncooked portion flow underneath. When the eggs are set, spoon avocado mixture over one side and sprinkle with cheese; fold other side over filling.
Invert omelet onto a plate to serve. Cover and let stand for 1-1/2 minutes or until cheese is melted. Serve with salsa if desired.