Creamy and comforting casserole, adapted from Laurel's Kitchen (Handbook to vegetarian cookery and nutrition). Suggested as a main dish but also a great holiday side dish (say, for Thanksgiving dinner). The original recipe calls for margarine instead of butter. Tip: When adding the milk to make the sauce, make sure that the milk is at room temperature or even slightly warmed, and be sure to add it *slowly*. This really makes a difference in how the sauce thickens up.