Cook pasta to the minimum time stated on the package to prevent it from overcooking while baking.
To thaw shrimp, place in a colander or strainer and rinse with cool water until it is thawed. Drain well.
To make ahead, prepare the casseroles without the topping. Cover tightly and refrigerate until ready to bake. Uncover casseroles and sprinkle with topping. Bake 25 to 30 minutes or until bubbly around edges.