Finely chop the onion and garlic and put in a large pan with a little cooking oil. Saute until soft.
Peel and roughly chop the carrots and parsnips. Add to the pan, along with the stock and bring to the boil. Add the lentils and herbs & spices, then put a lid on the pan and simmer until the vegetables are tender and the lentils are cooked (about 20 mins).
Preheat the oven to 140oC.
Use a slotted spoon to transfer the veg and lentils into a casserole dish, then ladle enough of the liquid to cover them completely. Add the kidney beans and stir in. Put into the oven and cook until a slight skin forms on the top and the casserole is bubbling (30-40 mins).
Meanwhile, make the mashed potato. Peel and chop the potatoes and place into a pan of boiling water. Simmer until the potatoes are completely tender.
Remove from heat and add the milk and butter to the pan. Mash and season with salt, pepper, and a few dried mixed herbs.
Carefully put spoonfuls of the mashed potato onto the vegetable casserole. Increase oven temp to 180oC and return casserole to oven until the potato is just beginning to crisp on the top. (20-30 mins).
Grate a small amount of hard cheese (mature cheddar is brilliant in this dish) over the potato.
Allow to cool slightly so that it is not scalding, then serve with warm, crusty bread.
Notes
- If you want to turn this vegetarian lentil casserole recipe into savoury, you can add meat to the recipe, such as chicken, lamb, turkey, or beef