Lots of quick and easy casseroles recipes here baked in the oven, in a pressure cooker or on the stovetop. using ground beef, leftover turkey or ham or pastas.
Melt half of your butter in a large pot over medium heat. Once melted, add the onions and cook until softened. Add the sliced mushrooms and cook until your desired color and texture.
Remove the onions and mushrooms to a small bowl. Place the rest of your butter in the pot. In another pot prepare the pasta according to package directions, boil until al dente.
Whisk the flour into the hot melted butter mixture to form a roux, then whisk in the milk. Season as you like but at least with a pinch of salt and pepper and cook for 8 minutes until thickened.
Stir in the broth, pasta, and cooked ham and cook until ham is warmed through. Set oven to broil. Pour the pasta mixture into an 8" x 8" casserole dish and sprinkle the grated cheese on top.
(French's fried onions on top is great too)Place the casserole dish in the oven and broil until cheese is golden and melted. (this step is optional)