Place all ingredients, except prawns and wonton wrappers, in a food processor and pulse until just combined and still slightly coarse in texture.
Place the wontons wrappers on a work surface. Brush the outer edges with cold water. Divide and mound an equal amount of the shrimp mixture in the centre of each wrapper. Push a prawn into the centre of the shrimp mixture, standing it tail side up. Lift up the corners of each wonton wrapper and gently squeeze the top to encase the shrimp mixture inside. Line a steamer with lettuce leaves. Set in the dumplings, they should not touch. Cover and steam over boiling water 5 minutes, or until just cooked through.