Cut up fresh broccoli and cook in boiling salted water for 10 to 15 minutes or cook frozen broccoli according to directions on package. Drain. Cook frozen or fresh onions in boiling salted water until tender. Drain. In a saucepan melt half of the butter, blend in flour, salt and pepper. Add milk, and cook stirring constantly, till thickened and bubbly. Reduce heat and blend in cream cheese till smooth. Place vegetables in a 1 1/2 quart casserole. Pour sauce mixture over and mix lightly. Top with American cheese. Melt the remaining butter and toss with the bread crumbs. Sprinkle over the casserole. Bake at 350 degrees 40 to 45 minutes or until heated through. Serves 6