Prawns are a satiating, low-fat source of protein, so a prawn curry is a much better choice for your waistline than, say, a chicken tikka masala. Heat some oil in a saucepan, then add 1 tsp mustard seeds and a sliced onion, cooking until golden. Mix in some finely chopped garlic and ginger, cook for two minutes, then tip in a can of chopped tomatoes. Cover and simmer on low for 15 minutes, blend the sauce, then cook for another 10 minutes. Stir in 1 tsp ground coriander and 1/2 tsp each turmeric, garam masala, chilli powder and salt. Add 12 raw king prawns and cook until pink. Stir in a tablespoon of whipping cream for a silky finish.