Cook spinach and onion according to package directions. Drain well, pressing out excess liquid. In a bowl combine eggs, cheeses, salad dressing, margarine, and garlic powder. Stir in spinach and muffin mix. Cover, chill 1 hour or till easy to handle. Shape into 1-inch balls; arrange on a baking sheet. Cover; chill till serving time. (Or, place in a freezer container; seal, label, and freeze.) To serve, place puffs on baking sheet. Bake in 350° oven 10 to 12 minutes for chilled puffs or 12 to 15 minutes for frozen puffs or till light brown. Serve warm with mustard. Makes 50. Nutrition information per puff: 47 cal , 2 g pro., 4 g carbo., 3 g fat, 17 mg chol, 111 mg sodium. appet 70