01 - Whisk eggs, milk, salt, and pepper in a medium bowl until fully blended.
02 - Heat half the butter in a large nonstick skillet over medium heat. Add chopped spinach and sauté for 1 minute until wilted.
03 - Reduce heat to medium-low. Pour in the egg mixture. Stir frequently, cooking until eggs are softly set. Remove from heat.
04 - Sprinkle a quarter of the shredded cheese over half of each tortilla. Top with a portion of the scrambled egg and spinach mixture. Add remaining cheese and fold each tortilla over.
05 - Wipe skillet clean and melt remaining butter over medium heat. Cook each folded quesadilla for 2 to 3 minutes per side until golden brown and cheese is melted.
06 - Transfer quesadillas to a cutting board. Slice into wedges and serve warm.