Shepherdless pie

I often make a meatless version of Shepherd's Pie; Bean is vegetarian, and it doesn't do the rest of us any harm to have meatless meals a couple of times a week. I occasionally use Quorn mince or similar, but prefer to use vegetables, etc. This is one of my favourite incarnations, using green lentils. Serves 4 with hearty appetites!

8oz or so of green lentils
1 large carrot, diced
1 medium onion, chopped fine
mushroom ketchup
tomato puree
mixed herbs, fresh or dried
4 - 6 large potatoes
milk, butter and seasoning to mash

Put lentils, onion and carrot in a pan, and just cover with water; bring to the boil, then leave to simmer until lentils are tender, when the carrot and onion should be cooked too. Meanwhile, peel and boil potatoes until tender, drain and mash with milk, butter and seasoning.
Add a good spoonful of mushroom ketchup, about a tablespoon of tomato puree and a good pinch of herbs to the lentils, mix thoroughly and put into pie dish. Top with mashed potatoes and bake in a hot oven until golden and crisp on top. If you like, grated cheese can be sprinkled over the potato. A vegan version can be made by using olive oil in the potato instead of butter and milk.
Serve with plain seasonal vegetables - we're having braised leeks tonight.