Italian Shells Casserole

2 pounds medium-size shells
1 teaspoon salt
16 ounces sour cream
16 ounces provolone cheese, sliced
2 pounds ground beef
2 to 3 quarts spaghetti sauce (your own or pre-made)
1/2 teaspoon pepper
24 to 32 ounces shredded mozzarella cheese

Cook shells. Rinse, drain and set aside.

Brown ground beef. Add salt, pepper and spaghetti sauce. Simmer for 20 minutes.

Spray deep lasagna pan or large casserole dish with nonstick spray. Line with half of the shells. Cover shells with half the meat sauce. Spread half the sour cream over it and cover with half of both cheeses. Repeat for the second layer. Cover with lid or foil and bake at 350 degrees F for 40 minutes.

Uncover and bake 20 minutes more.

Serve hot.