Peel and chop potatoes into small pieces and put in large saucepan of boiling water for 15 minutes. While potatoes are cooking simmer red lentils in a small saucepan with vegetable stock and a splash of wine.
Chop carrots, onion and celery and add to a large saucepan with butter and garlic. Cook until soft.
Add lentils (which will have absorbed all the stock) to pan with vegetables and add tomato puree. Turn heat down to a simmer while you mash the potatoes with butter and plenty of pepper.
Add lentil mix into a glass dish and top with the mashed potatoes. Cook for 30-40 minutes in a 200 degree C oven, or until potato top is browned nicely.