MIX mayonnaise, lime juice and sriracha. Mix hoisin sauce and vinegar in separate bowl.

COMBINE lemon grass, ginger, salt and pepper in shallow pan. Dip fish in lemon grass mixture, turning to evenly coat both sides of each piece. Heat oil in skillet on high heat until oil starts to smoke. Add fish; cook 1 to 2 min. on each side or until fish pieces are golden brown and flake easily with fork.

MEANWHILE, deep fry potatoes as directed on package; drain.

FOR each portion, 2 servings: Plate 4 oz. potatoes; top with 5 fish pieces. Drizzle with 3 Tbsp. of the mayonnaise mixture and 1/4 cup of the hoisin sauce mixture. Sprinkle with 2 Tbsp. onions.