Cauliflower Pasta Casserole

(a variation of a recipe called Cauliflower Cheese Pasta, from Jean Paré's pasta cookbook)

2 c pasta, any kind but spaghetti
boiling water
1/2 c chopped green pepper
1/2 medium onion, chopped
1 c sliced fresh mushrooms
5 tb butter
3 tb white flour
1 tsp salt
1/8 tsp pepper
1 and 1/2 c milk
1 c grated cheddar cheese
2 c coarsely chopped cauliflower
1/2 c breadcrumbs
2 tb butter

Preheat oven to 350F.
Boil pasta and set aside. Steam cauliflower at medium heat about 8 minutes or until tender, in a half-inch of boiling water. Drain both and mix together. (You can cook them together in one pot as long as your cauliflower is coarsely enough chopped). Sauté onion, pepper and mushrooms in a tablespoon of butter in another pot, then add to the pasta and cauliflower and set aside.
Melt 3 tb butter in pot, add salt, pepper and flour, stir over medium heat and add milk. Stir until sauce comes to a boil and thickens; add grated cheese. Mix with veggies and put into greased casserole dish.
Melt 1 tb butter and stir in bread crumbs. Sprinkle on top of mixture in casserole and bake uncovered for 25 minutes.
If you have no bread crumbs handy, sprinkle top of casserole with chili powder.
Double this recipe if you have teenagers.