Heat oil in a pan on medium heat. Add the cloves and cardamom to infuse for a minute before adding the diced onion. When the onion is softened and brown add the cumin, coriander and turmeric. Allow spices to cook through with the onions for 2-3 minutes before adding the garlic and chilli. Turn the heat up, add the lamb mince, and brown for 10 minutes, stirring occasionally. Add the peas and tomatoes followed by the stock. Put a lid on the pan, reduce the heat to low and leave to simmer for an hour.
Boil the potatoes in a pan of salted boiling water until soft and tender. Once cooked, sieve and leave to cool slightly before peeling and mashing until smooth. Add the rest of the ingredients and mix well to combine. Add salt to taste.
Preheat the oven to 190°C/375°F/gas 5. Transfer the lamb mixture to a large ovenproof baking dish. Season with salt before spooning the spiced mash evenly over the top. Cover with the grated cheddar. Cook in the hot oven for 25 minutes, or until golden and bubbling.