01 -  Combine eggs, milk, salt, and black pepper in a mixing bowl. Whisk until thoroughly blended and slightly frothy. 
 02 -  Melt butter in a nonstick skillet over medium heat. Pour in egg mixture and cook, stirring gently with a spatula, until eggs are softly set but not fully dry. Transfer eggs to a plate. 
 03 -  Slice avocado and place into a small bowl. Lightly mash with a fork, adding a pinch of salt and chili flakes if desired. 
 04 -  Lay tortillas flat. Sprinkle half of the cheddar cheese on one side of each tortilla. Arrange scrambled eggs, mashed avocado, and cilantro (if using) evenly on top. Scatter remaining cheese over the filling. Fold tortillas over to create a half-moon shape, sealing the filling inside. 
 05 -  Wipe out the skillet and warm over medium heat. Cook quesadillas one at a time for 2 to 3 minutes per side, until the tortillas are golden and the cheese is fully melted. 
 06 -  Transfer quesadillas to a cutting board, allow to cool slightly, then slice each into wedges. Serve warm with salsa, sour cream, or hot sauce as preferred.