Indian spice box chicken - Good Food Middle East

Ingredients

• 50g fat green mild chillies (about 3 large ones)
• 3 large garlic cloves
• 5cm piece of fresh root ginger
• a bunch of fresh coriander
• 200g carton of full-fat Greek yogurt
• 2 medium onions
• 8 medium bone-in chicken thighs (total weight about 800g-1kg/1lb 12oz-2lb 4oz)
• 2 tbsp groundnut or corn oil
• 2 tsp fennel seeds
• 1 tsp cumin seeds
• a good knob of butter
• Chilli-ginger garnish, to serve (see below)