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 ginger root.
Add brown sugar, curry, pepper, salt, fish sauce, and 1 cup of the coconut milk and puree.
Quarter each hen and divide the hen between 2 large plastic zip lock bags and divide the marinade and seal the bags, pressing out all air.
Put bags in a large shallow dish and marinate hens, chilled, turning bag once or twice overnight.
Preheat oven to 450 degrees F. and line a large shallow roasting pan with foil.
Remove hens from the marinade, reserving marinade, and arrange hens, skin side up, in the prepared pan. Roast 20-25 minutes until cooked through.
While hens are roasting, in a small saucepan, combine reserved marinade and remaining 1 cup of coconut milk and cook sauce at a slow boil, stirring occasionally, 5 minutes, and strain through a sieve into another small saucepan to keep warm.
Serve hens with the marinade sauce and/or the Sweet Chili Sauce.
For the Sweet Chili sauce, in a small saucepan, combine all ingredients and simmer, stirring occasionally, 10 minutes. Cool sauce to room temperature. Sauce may be made up to 3 days ahead and kept chilled, covered. Serve at room temperature though. (Yield: 1 1/2 cups).