1.Blend or process chopped lemongrass, ginger, garlic, oil, sauce and juice until smooth. Stir in onion.
2.Place long piece of baking paper on bench; place fish on paper. Fill cavity with lemongrass mixture.
3.Score fish three times both sides through thickest part of flesh, seal cuts with lime slices; sprinkle fish with sliced lemon grass and lime leaf. Fold paper over fish to completely enclose, then wrap fish tightly in foil.
4.Cook fish on heated oiled grill plate (or grill or barbecue) 25 minutes; turn, cook about 20 minutes or until cooked through.
5.Serve fish sprinkled with coriander; serve with lime wedges.