Step 1

To make chilli coriander dressing, whisk all ingredients in a small bowl until combined.

Step 2

Remove heads and legs from prawns, leaving tail and back shell intact. Split the prawns along the underside to open out flat, leaving shells on.

Step 3

Cook lime halves on a heated, oiled grill plate (or grill or barbecue) until browned lightly; remove. Brush prawns with oil; cook prawns on same grill plate until browned and cooked through.

Step 4

Serve prawns with watercress. Drizzle with chilli coriander dressing and serve with limes.