One-pot prawn & lentil curry

Name: One-pot prawn & lentil curry
Prep time: 30 min
Cook time: 1 h 15 min
Total time: 1 h 45 min
Cuisine: Asian, Indian
Ingredients: 100g dried red lentils; 3 tbsp sunflower oil; 1 large onion, finely chopped; 6 garlic cloves, chopped or grated; thumb-sized piece of ginger, peeled and chopped or grated; ¼ tsp ground turmeric; ¼ tsp chilli powder (we used Kashmiri chilli powder); 1 tbsp cumin seeds; 1 tbsp ground coriander; 1 tbsp tomato purée; 1 tsp tamarind paste or lemon juice (optional); 400g can chopped tomatoes or passata; 1 chicken or vegetable stock cube; 1 tbsp garam marsala; 200g raw or cooked prawns (we used tiger prawns); green chillies, coriander and pickled red onions (see tips), to serve