PreparationMake marinade: Thinly slice lower 6 inches of lemongrass stalks, discarding remainder of stalks In a food processor or blender finely grind together sliced lemongrass, coriander, shallot, garlic, and gingerroot. Add sugar, curry powder, pepper, salt, fish sauce, and 1 cup coconut milk and purée. Quarter each hen and divide between 2 large resealable plastic bags. Divide marinade between bags and seal bags, pressing out excess air. Put bags in large shallow dish and marinate hens, chilled, turning bag once or twice, overnight. Preheat oven to 450°F. and line a large shallow roasting pan with foil. Remove hens from marinade, reserving marinade, and arranged hens, skin sides up, in prepared pan. Roast hens 20 to 25 minutes, or until just cooked through. While hens are roasting, in a small saucepan combine reserved marinade and remaining 1 cup coconut milk. Cook sauce at a slow boil, stirring occasionally, 5 minutes and strain through a fine sieve into another small saucepan to keep warm. Serve hens with marinade sauce and/or sweet chili sauce for dipping if desired.