Preheat oven to 425°F.
Heat a large, nonstick, oven-safe skillet over medium-high heat. If all of your skillets have rubber handles, cover handle tightly in foil to protect it. Add oil and butter, and melt together. Add the leftover pasta and cook until lightly browned, 2-3 minutes.
While the pasta is browning, beat the eggs with the half-and-half, add some salt, pepper and the parsley.
Add the egg mixture to the skillet and stir gently to combine. Allow the eggs to set up on the bottom of the pan and become firm. Top with the leftover tomato sauce and then the cheese. Transfer pan to the oven and bake for 10 minutes, until golden. Serve hot or cold from the pan or transfer to a platter, cutting frittata into wedges. If it's for lunch or dinner, serve with a simple salad.