In a small bowl, whisk together the mayonnaise, mango chutney, hot pepper sauce, lime juice, and turmeric until smooth and golden. Season with a pinch of sea salt. Cover and refrigerate until needed — the longer it sits, the better the flavours meld.
In a large bowl, combine the plain flour, baking powder, desiccated coconut, ground allspice, garlic powder, salt, and pepper. Make a well in the centre, then add the beaten egg and coconut milk. Stir together until you have a thick, smooth batter.
Fold in the roughly chopped raw prawns, sliced spring onions, chopped red chilli, and lime zest. Mix gently until everything is evenly distributed throughout the batter.
Pour sunflower oil into a deep frying pan to a depth of about 2cm. Heat over medium-high heat until a small drop of batter sizzles and rises to the surface immediately — approximately 175°C.
Working in batches, drop heaped tablespoons of the prawn batter into the hot oil. Fry no more than 5–6 fritters at a time. Cook for 2–3 minutes per side until deeply golden and cooked through.
Remove with a slotted spoon and drain on a plate lined with kitchen paper. Season with a tiny pinch of salt immediately while still hot.
Arrange the fritters on a serving platter, dust lightly with cayenne pepper, scatter sliced spring onions over the top, and serve immediately alongside the Calypso dipping sauce and fresh lime wedges.