Cook pasta according to directions, drain and set aside. Don't overcook the pasta.
Mix together Alfredo sauce, sour cream, Parmesan cheese, and pepper in a pot. Stir constantly while letting all that goodness heat up and melt together.
Lay all the pasta in a 9 x 13 pan. Sprinkle mozzarella cheese on top of pasta and then pour Alfredo mixture on top of that. Sprinkle with more Parmesan cheese.
Cover tightly with foil and bake 30 minutes in a 350-degree oven. Remove foil and bake for another 10 minutes or so until the top just starts to turn a golden brown.