01 -
Preheat the oven to 375°F (190°C). In a bowl, whisk together the eggs, milk, salt, pepper, and thyme. Set aside.
02 -
Heat olive oil and butter in an oven-safe skillet over medium heat. Add the leeks and cook for 3-4 minutes, stirring until softened. Stir in the asparagus and cook for another 2 minutes until slightly tender.
03 -
Pour the egg mixture over the sautéed vegetables. Gently dollop ricotta cheese on top. Sprinkle with Parmesan cheese and red pepper flakes, if using.
04 -
Transfer the skillet to the preheated oven and bake for 15-18 minutes, or until the eggs are set in the center and lightly golden on top.
05 -
Let the frittata cool slightly before slicing. Serve warm with a side salad or crusty bread.