1. Preheat the grill to medium-high. In a large bowl, toss prawns in oil and season with salt and pepper. Grill the prawns for 1 to 2 minutes on each side or until just cooked through. Be careful not to overcook the shrimp, or they will be tough and rubbery. Remove from the grill.
2. Place about 3 prawns in each lettuce leaf. Drizzle with the Serrano-Mint Sauce and with a little chili oil, if desired. Sprinkle with a few coriander leaves. Roll up the lettuce leaves, and eat immediately.
1. Pulse until smooth. Season, to taste.