In medium bowl, beat eggs and cooking sauce with whisk until well mixed.
In 10-inch nonstick skillet, melt butter over medium heat just until butter begins to sizzle. Pour egg mixture into skillet. As mixture begins to set at bottom and side, gently lift cooked portions with spatula so that thin, uncooked portion can flow to bottom. Avoid constant stirring. Cook 3 to 4 minutes or until eggs are thickened throughout but still moist.
Meanwhile, heat taco shells as directed on box. Spoon about 1/4 cup of the egg mixture and 2 tablespoons cheese into each taco shell. Top with avocado, salsa and sour cream.