Warm the vegetable oil in a casserole pan set over medium heat. Add the diced onion, carrot and a pinch of salt and sweat for 5 minutes, until softened. Add the lamb mince and cook for about 5 minutes, stirring occasionally to break up the meat. Add the flour, mix well and cook for a further 1 minute.

Next add the tomato puree, lamb stock, Worcestershire sauce and the baked beans. Bring to the boil then reduce the heat and simmer for 20 minutes, until thick and glossy. Taste and adjust the seasoning as needed.

Whilst the sauce is cooking, preheat the oven to 200°C/180°C fan. Heat mashed potato according to the manufactures instructions. Doing this will make it easy to spread in the next step.

To assemble your shepherds pie you will need a deep-sided baking dish approx. 20x30cm. Tip the cooked lamb into the dish and spread out across the bottom. Top with the mashed potato and smooth into an even layer. Use the back of a spoon to make swirls in the potato, or a fork to make ridges – this will give you lovely crispy bits of potato. If using, scatter over grated cheddar at this stage. Bake for 30 minutes, until golden and bubbling.