turkey tetrazzini recipe

Ingredients: 12 oz spaghetti or fettuccine 4 tablespoons unsalted butter, divided 1 small onion, finely chopped 2 cloves garlic, minced 1/4 cup all-purpose flour 2 cups chicken or turkey broth 1 cup heavy cream 1/2 cup grated Parmesan cheese 3 cups cooked turkey, shredded or diced