1. Cut roots and leafy tops off lemon grass stalks.
2. In a mortar and pestle, pound lemongrass, salt, garlic, turmeric, and pepper into a fine paste.
3. Cut open chicken lengthwise. Separate into 2 pieces, and rinse well. Rub chicken with mixed spice paste. Marinate in refrigerator for 4 hours or overnight.
4. Grill over moderate heat for 10 to 15 minutes, or until well done and evenly brown. Serve hot.