Prawn Marinade: Stir together all the marinade ingredients in a large bowl.
Add the prawns and coat in the marinade then let marinate for 20 to 30 minutes.
Preheat the barbecue to medium-high heat.
Sauce: Pour all the sauce ingredients except the peanut oil, mint, coriander and peanuts, into a food processor or blender and process until smooth. While processing, slowly pour in the peanut oil and keep processing until the sauce is smooth and creamy.
Pour into a bowl, stir in mint, coriander and peanuts then season to taste with salt.
To Serve: Remove the prawns from marinade, shaking off any excess. Cook on the preheated barbecue until pink and firm, about 2 minutes per side. Serve immediately with the sauce.