1Add chicken, peppers, onion, passata, tikka paste, garlic, herbs, curry powder, and food coloring to a slow cooker. Cook for 4 hours on high or 6 on low.
2Stir in yoghurt 30 minutes before serving.
3If using a pan, fry chicken, onion, and pepper until cooked. Add tikka paste and spices, simmer until thickened. Reduce heat and stir in yoghurt.
4Preheat oven to 180 degrees (fan) about half an hour before serving.
5Mix yoghurt, flour, garlic granules, and herbs for the naan crust. Divide in two and roll out to fit ramekins.
6Add curry to ramekins and top with naan crust. Brush with garlic butter.