Grilled Prawns (Vietnam)

1 small onion, minced
2 cloves garlic, minced
1 teaspoon peanut oil
1 pound jumbo shrimp or king prawns
1 teaspoon sea salt
1 teaspoon freshly-ground black pepper
Juice of 2 limes
1 tablespoon peanut butter

Mix the onion and garlic with peanut oil. Add the prawns and toss to coat. Leave to marinate for at least three hours or overnight.

Grill the prawns or broil them for about 5 minutes, turning once. Whisk together the remaining ingredients to make the sauce and pour it into a small sauce bowl, placed at the center of the platter of prawns.

Serves 4.