794ml/28fl oz water or fish stock
2 medium onions, peeled and finely chopped
1 tbsp finely grated ginger
4 garlic cloves, peeled and crushed
1 red chilli, deseeded and finely sliced
pinch of turmeric
1 tsp each of mild curry powder, ground coriander, mild chilli powder and ground cumin
1 level tbsp tamarind pasta (optional)
397g/14oz sweet potato flesh, cut into 2.5cm/1in pieces or large bite-sized cubes
1 large red pepper, deseeded and cut into bite-sized pieces
794g/1lb 12oz raw tiger prawns, peeled but with tails left on
255g/9oz sugar snap peas, trimmed
 salt and freshly ground black pepper
1. Heat 100ml/3½ fl oz of the water or stock in a large saucepan, add the onions and cook over a medium heat for 4-5 minutes or until softened. Add the ginger, garlic and red chilli and stir and cook for 1-2 minutes. Add the turmeric, curry powder, ground coriander, chilli powder and ground cumin and stir and cook for 1-2 minutes.
2. Add the tamarind paste, if using, and the remaining water or stock and bring to the boil. Add the sweet potato and red pepper, bring back to the boil, reduce the heat to low and simmer gently for 15-20 minutes.
3. Add the prawns to the curry with the sugar snap peas and cook over a high heat for 4-5 minutes or until the prawns turn pink and are just cooked through and the vegetables are tender. Season well and remove from the heat.
4. Serve immediately in four warmed bowls.