Quiche is usually my go-to for transforming leftovers into an incredible breakfast and by adding leftover spaghetti the dish becomes easier to make (no pesky pastry crust!) and heartier to start the day.
Preheat oven to 375 F. Then, brush oven-safe skillet with butter and set aside until needed.
Next, cook the spaghetti, according to the package instructions. When done, drain and return to the pot. If you are using leftover spaghetti, skip this step.
Then add 1 tbsp of the butter and stir till melted. Further, add the marinara sauce and the Parmesan, stir to combine. When fully combined, transfer the spaghetti to the prepared baking dish.
After that, whisk eggs, heavy cream, milk, butter, basil, salt and pepper in a bowl. Pour the mixture over the spaghetti. (At this moment, you can add any kind of topping you like, vegetables, bacon, cheese...)
Transfer it to the oven and bake for 35 minutes. Then, turn the broiler on, and heat the quiche until golden on top.