Mix the lime juice with the mayonnaise and set aside.
Heat the oil in a large, non-stick frying pan over a medium heat and add the garlic, ginger and chilli. Lightly fry for 2 mins until fragrant, then add the tamarind paste.
Toss the prawns in the mixture and cook for 2-3 mins until they have all turned pink. Serve with rice topped with the sesame seeds and spring onions, and the lime mayo, plus lime wedges for squeezing over.