In a large nonstick skillet, over medium heat, melt the butter.
Meanwhile, in a large bowl, whisk together the eggs, the milk or water, the salt, and the pepper. Pour the mixture into the pan and cook, stirring occasionally, to desired doneness, 4 to 5 minutes. Just before the eggs are set, fold in the cheese. When the eggs are cooked, stir in the salsa and the tortilla chips.