Leftover lamb curry

Name: Leftover lamb curry
Ingredients: 2 onions, roughly chopped; 1 large garlic clove, chopped; 1 thumb sized piece ginger, peeled and chopped; 2 tbsp oil; 4 tbsp medium curry paste; 400g can chopped tomatoes; 1 red chilli, halved and seeds removed; 1 cinnamon stick; 200ml lamb stock; 500-700g leftover roast lamb, chopped into large chunks; 1 small bunch of coriander, roughly chopped; cooked basmati rice, naan bread and natural yogurt, to serve