Chicken tikka masala

Name: Chicken tikka masala
Ingredients: 2 tbsp. vegetable oil; 2 large onions, finely sliced; 500 g (1lb 2oz) chicken thigh fillets, cut into bite-size pieces; 400 g (14oz) tin chopped tomatoes; 150 g (5oz) natural yogurt; 150 mL (5 fl oz (¼ pint)) double cream; 5 cardamon pods; 5 garlic cloves, peeled and chopped; 5cm (2in) piece fresh root ginger, peeled and chopped; 1 red chilli, deseeded and chopped; 2 tsp. each ground coriander and cumin; 1 tsp. each paprika, garam masala and turmeric