Heat the oil in a frying pan over a low-medium heat. Add the onion and cook for 15 mins until soft and starting to caramelise, stirring regularly. Add the garlic, ginger, tomatoes and the chilli, if using. Turn the heat up to medium and cook for another 10 mins.

Meanwhile, if you’re using shell-on prawns, prepare them now. Remove the head and, using a pair of scissors, cut down the back of the shell until you reach the last segment of shell that’s attached to the tail. Cut through the top layer of flesh on the back of each prawn so it’s easy to remove the vein – loosen it from the body, then with your fingers as close to the tail as possible, pull gently to remove the vein completely. You can keep the heads and shells to make a stock.

Mix the ground spices and tamarind paste with 2 tbsp water, then add to the onion mix. Cook for 5 mins until the spices are fragrant and most of the water has evaporated.

Stir in the coconut milk and cook for 5-10 mins until reduced to a thick gravy, then tip in the prawns. Cook for 5 mins until they are just pink, then remove from the heat. Serve with rice.