To the slow cooker, add the onion, garlic, ginger, lamb pieces, tomato paste, curry paste, tinned tomatoes, chicken stock and water. Stir well to combine. Place the lid on and cook for 3 hours on high or 7 hours on low.
1 brown onion, 3 cloves garlic, 3 cm ginger piece, 1 kg lamb leg, 2 tbsp tomato paste, 3 tbsp rogan josh curry paste, 400 g canned diced tomatoes, 1 chicken stock cube, 1 cup water