Tofu has become a big business in this country, as more and more health-conscious Americans are beginning to think that this low-cholesterol, high-protein soy product might be more than just hippie food. Paino, founder of a large tofu company, and his coauthor have written an enthusiastic guide to tofu, along with recipes for all courses of a meal. The recipes are meant to demonstrate tofu's versatility, but some seem ill-conceived (Filet de Tofu with Apricot Dijon Sauce) and the techniques are sometimes questionable. For special collections. Yogurt, on the other hand, is by now a familiar ingredient to a wide variety of good cooks, as Hirshberg's book demonstrates. Here are 300 of the best yogurt recipes submitted for a contest sponsored by Stonyfield Farm or in answer to an appeal in Harrowsmith Country Life : delicious waffles and pancakes, main dishes of all sorts, a wide variety of desserts and baked goods. Some are homey comfort food, some more sophisticated offerings inspired by the various ethnic cuisines in which yogurt is a staple. For larger collections.