Boil the potatoes until cooked through, for around 30 minutes. Drain the potatoes and leave them to cool.
Preheat the oven to 180C/356F. Heat the oil in a large pan over a medium heat. Add the onion, carrot, peppers and garlic, and sauté for 10 mins over a medium heat.
Add the lamb mince and the boiling water to the pan and use a wooden spoon or spatula to break it up. Cook until well browned and all of the water has been evaporated, stirring regularly.
Add the tomato paste, paprika, cumin, black pepper, thyme, rosemary and 1 tsp of the salt. Mix everything together well, cover with a lid and simmer for 10 mins, stirring from time to time.
Crush the potatoes with a potato masher or a fork until smooth. Add the remaining salt and olive oil, and mix until fluffy and well blended.
Pour the lamb mixture into an oven-proof casserole dish. Spoon the mashed potato on top and use a fork to spread it around, sealing in the meat.
Bake in the oven for 40-45 minutes until the potato is crisp and golden on top. Enjoy!