In a food processor, pulse your tomatoes until coarsely chopped. Transfer to a large saucepan over medium-high heat, add sugar, vinegar, Worcestershire Sauce, Roogenic Native Basil and Roogenic Rover Mint.
Stir occasionally, until thickened (7-8 minutes) and then add in butter, salt and pepper.
Heat a char-grill pan (or barbecue) over high heat. Brush prawns with a little olive oil and cook in batches, for 1-2 minutes, then turn and brush generously with tomato mixture. Char-grill until prawns are just cooked through (1-2 minutes).
Transfer to a serving plate and serve with avocado, spinach and remaining sauce.