Cottage pie and shepherds pie are so wonderful, it's no wonder vegans want their own version. This one is based around a savoury sauce of lentils, barley and mushrooms.
Rinse the mushrooms and finely chop half of them. Chop the remainder more coarsely so you get a variation in texture. Heat some oil on medium-low heat in a large frying pan and add the mushrooms. Cook them for about 10 minutes - when they start to release their moisture turn up the heat a little to make it evaporate. Remove the mushrooms from the pan and set aside.
While the mushrooms are cooking, peel and chop the onion and dice the carrot. Heat some more oil in the frying pan. Sauté the onions for about 5 minutes - it's OK to get a bit of browning on the edges. Add the onions and cook for a couple of minutes and then add the stock, the lentils, the drained barley and the mushrooms. Give it all a good stir then add the yeast extract, vegan 'Worcester' sauce, tomato puree and most of the chopped parsley (save a bit for garnish). Let it simmer for 20-25 minutes until the lentils have cooked down to a mush. Season with salt and pepper if required then remove from heat and transfer it to the ovenproof dish you plan to bake it in. Allow the sauce to cool down and firm up a little.
Put the pie in the oven and bake for about 25 minutes until the top is golden.
† Vegan substitutes: butter is obviously a vegan no-no because of its dairy content, but oil-based margarines/spreads are usually OK - check the packaging says something like 'suitable for vegans'. Most Worcester-type sauces contain anchovies or fish sauce. Look for alternatives that don't - Henderson's Relish is vegan friendly. You might also look at things like HP Sauce, tamarind, soy sauce.