Butter chicken recipe

Ingredients

• 2 large white onions, cut in half and thinly sliced
• 5 cm/2 inch piece of fresh root ginger, peeled and grated
• 6 garlic cloves, grated
• 2 tsp ground cumin
• 2 tsp ground coriander
• 1/2 tsp ground cardamom
• 1/2 tsp ground cinnamon
• 0.2 tsp ground fenugreek
• 1/2 tsp ground turmeric
• 0.2 tsp chilli powder
• 2 tbsp tomato purée/paste
• 400 g can chopped tomatoes
• 5 tbsp Greek-style yogurt
• 750 g bone-in chicken thighs, diced
• 2 tbsp tandoori masala
• 2 tsp salt
• 1 tsp sugar
• 80 g butter
• 5 tbsp vegetable oil