-Velveeta Shells & Cheese) Prep time: 5 minutes; Cooking time: 40 minutes plus standing. Heat oven to 375'F. Mix water and mustard in 1 1/2 quart casserole dish. Whisk in Cheese Sauce from Pouch. Stir in dry Pasta; cover with tight-fitting lid. Bake 30 minutes. Uncover. Stir in sour cream. Continue baking, uncovered, 10 minutes. Let stand 5 minutes before serving. Makes 6 servings. STIR-IN IDEAS: Reduce water to 2 cups (reduce water to 1 1/4 cups for Velveeta Shells & Cheese). Add 1 cup chopped cooked broccoli and 1 cup chopped ham OR 1 cup cooked peas and 1 cup chopped cooked chicken when stirring in sour cream. Continue as directed above. VARIATIONS: Top with combined 1/2 crushed crackers and 1 tablespoon melted margarine after stirring in sour cream. Continue as directed above. Substitute lowfat OR nonfat sour cream for regular sour cream.