Combine the first 7 ingredients in a bowl. Add the prawns and toss to coat. Cover and marinate for 20 minutes. Preheat an indoor or outdoor grill to medium-high. Thread the prawns on one end of the skewers; season with salt and pepper. Grill the prawns for 2 to 3 minutes per side, or until just cooked through. Arrange on a platter, garnish with lemon slices and serve.