If you want to remove completely the meat from this dish, add an extra 100g of lentils or some barley to the mixture with an extra 200ml of stock. This will help to bulk the pie.
Heat the oil in a sauté pan over high heat. Add the minced beef or lamb or cook for 2-3 minutes until coloured. Add the onions, carrots, garlic, mushroom and saute for 3–5 minutes until the onion are just beginning to colour.
Stir the lentils into the pan. Add the tomato puree, curry powder and the stock and bring to simmer with a lid on for 15-20 minutes or until completely tender.
Place the mixture in an ovenproof casserole dish. Pipe or spoon the mashed potato on the top of the mixture.
Bake in the oven for another 20–25 minutes until the mixture is bubbling hot and the topping is golden brown.
Serve immediately with some crisp green salad leaves.