Clean and wash spring onions and cut into fine rings. Clean, wash and cut the chilli into rings. Peel mangos, flesh tightly from the stone
Mix vinegar, 1/4 tsp salt, 1/4 tsp pepper and sugar. Fold in 6 tablespoons of oil. Mix mangoes, chilli, spring onions and vinaigrette. Mix sour cream and mayonnaise, season with salt and pepper.
Wash the prawns, dab dry with kitchen paper. Heat 2-3 tablespoons of oil in a frying pan. Add the prawns and fry them for about 2 minutes, turning them over. Season with salt and pepper.
Cut cress from the bed. Fill mango salsa into glasses. Put a blob of sour cream on each. Place one shrimp in each jar and sprinkle with cress.