How to Make It
Place a rack in the center of the oven and preheat to 375°F. Generously brush a 10-inch oven-safe skillet or 10-inch pie dish with butter and set aside.
Make the spaghetti. Cook the pasta al dente, according to the package instructions. Drain and return to the pot. Add 1 tablespoon butter and stir until melted. Add the marinara sauce and cheese, and stir well. Transfer to the prepared baking dish, without packing it down too much.
Make the quiche. In a medium bowl, whisk together the eggs, cream, milk, butter, basil, salt, and pepper. Pour the mixture over the spaghetti.
Bake 30 to 35 minutes, until the quiche is set and no longer jiggling. Turn on the oven broiler and heat the quiche under the broiler up to 5 minutes, until the top is golden. Let stand for 15 minutes. Sprinkle with basil before serving. This quiche is delicious served warm, at room temperature, or chilled.