Crush garlic, then tomatoes with a pinch of sea salt flakes with a large wooden mortar and pestle, or in a bowl. Add prawns and pound to crush, then add beans, chillies, peanuts and lime, and pound. Add papaya and bruise – do not overwork. Season with palm sugar, lime juice, tamarind water, fish sauce and chilli powder to taste – it should be sweet and sour, hot and salty – and serve.