One good trick I've tried for frugal cooking is to use a 'Sabbath hay-box'. It's simply a cardboard box, lined on all sides with good insulating material - I used 1/2" polystyrene sheets. You heat up a stew or casserole to a rolling boil on the stove, then put it in the box. Fill up any air-space with an old fleece, put another sheet of polystyrene on top, and close the box. The stew will continue to cook for hours if the insulation is done properly, it won't boil dry or burn, and you use no more fuel.