Cut racks into ribs. Place in pot with water to cover. Simmer, covered, 40 minutes; skim fat. Drain.
In saucepan, sauté onion and garlic in oil 5 minutes. Add ginger; cook 1 minute. Add preserves, vinegar, sugar, schnapps, pepper flakes; cook, stirring, 10 minutes.
In cup, mix cornstarch, water. Stir into sauce; boil 1 minute to thicken. Remove from heat; stir in soy.
Prepare grill with hot coals, or heat gas grill. (Or cook using oven method, below.) Brush grid with oil. Set aside 1/2 cup sauce. Brush ribs with remaining sauce.
Grill ribs 5 minutes. Turn over; brush with sauce. Grill 5 minutes. Makes 12 servings.
Coat broiler pan with spray. Brush cooked ribs with sauce. Broil 6 inches from heat 10 minutes, turning once and brushing with sauce.