Put the cardamom pods, cinnamon and bay in a pan over a medium heat, add the oil and lightly fry until fragrant, about 1 min. Add the onions, ginger & garlic paste and chillies, and cook for 5 mins. Add the mince and the remaining spices, and cook for 10-15 mins more until browned. Take off the heat and add the lime juice, then season.
Heat oven to 200C/180C fan/gas 4. Brush the naans with the butter, then wrap in foil and warm in the oven. Top with the mince followed by the yogurt, tomatoes, chilli and coriander. Serve with green chutney.