- Make Ahead Directions: To freeze in individual servings and microwave later, prepare shells and sauce as directed above. Spoon into 6 small freezer and microwave-safe containers. Cover tightly; freeze up to 3 months. To thaw, place in refrigerator 8 hours or overnight. Keep refrigerated until ready to microwave. To cook, loosely cover microwave container. Microwave on Medium-High (70% power), 4 minutes.