Photograph: Lisa Linder
Heat the oil in a large non-stick saucepan. Add the mustard seeds and cover with a lid, once the popping subsides, add the curry leaves. Follow quickly with the garlic and cook for one minute, or until the garlic smells cooked.
Add the tomatoes, tomato purée, ground spices and some salt and cook, stirring occasionally, until the masala has released oil on the base of the pan.
Add the prawns, crème fraîche and a good splash of water and simmer until the prawns are cooked through, a matter of three to four minutes. Taste and adjust the seasoning, stir in the coriander and serve hot.