Spaghetti and canned tuna team up with mushrooms and Parmesan cheese in this delicious tuna tetrazzini casserole, a twist on the classic turkey tetrazzini.
Cook the spaghetti in boiling salted water following the package directions for al dente. Drain and set aside
Melt 2 tablespoons of butter in a large saucepan over low heat; blend in flour, salt, and pepper. Cook for 2 minutes, stirring constantly. Gradually stir the milk into the roux and continue stirring and cooking over low heat until thickened.
Stir 1/2 cup of Parmesan cheese into the sauce.
Add tuna, mushrooms, and spaghetti; blend well.
Transfer the pasta mixture to the prepared casserole; sprinkle with the remaining grated Parmesan cheese.
Melt the remaining 2 tablespoons of butter and toss with bread crumbs.
Sprinkle the bread crumbs over the top of the casserole.
Bake, uncovered, for about 25 to 30 minutes, or until the bread crumbs are browned and the casserole is bubbly around the edges.