Preheat the oven to 350°F (175°C) and grease a 9-inch pie plate.
In a mixing bowl combine the cooked and cooled spaghetti with the slightly beaten eggs and the Parmesan until the pasta is evenly coated.
Press the spaghetti mixture into the greased pie plate, mounding it slightly and pressing down the center to create room for the fillings while leaving a 1–2 inch rim to form the crust.
Spoon the sour cream into the center of the spaghetti crust, spreading it into the depression.
Top the sour cream with the cooked, crumbled, and drained ground beef, then spread the spaghetti sauce over the beef.
Sprinkle the shredded mozzarella evenly over the top.
Bake for 25 minutes, until the cheese is melted and the pie is heated through; let sit a few minutes before slicing and serving.