For the filling
- 3 tbsp olive oil
- 1 medium onion, finely chopped
- 2 celery sticks, thinly sliced
- 1 medium leek, cut into roughly 5mm/¼in slices
- 250g/9oz chestnut mushrooms, sliced or halved, depending on size
- 1 medium courgette, chopped
- 2 garlic cloves, crushed
- 2 carrots, chopped
- 400g tin chopped tomatoes
- 2 x 400g tins lentils, drained and rinsed
- 100ml/3½fl oz red wine (vegan-friendly) or water
- 2 tbsp tomato purée
- 2 tbsp yeast extract, such as Marmite
- 1 tsp dried mixed herbs
- 1 vegetable stock cube
- sea salt and ground black pepper
For the mash
- 1kg/2lb 4oz floury potatoes, ideally Maris Piper, peeled and cut into roughly 5cm/2in chunks
- 100ml/3½fl oz plant-based milk, such as almond or soya
- 3 tbsp extra virgin olive oil
- 2 tbsp nutritional yeast flakes
- To make the filling, heat the oil in a large, wide-based non-stick saucepan or sauté pan and gently fry the onion, celery and leek for 5 minutes, stirring regularly. Add the mushrooms and courgette and cook for a further 5 minutes, or until softened and lightly browned. Stir in the garlic and cook for a few seconds more.
- Add the carrots, tomatoes, drained lentils, 300ml/10fl oz water, wine (or extra water), tomato purée, yeast extract, mixed herbs and crumbled stock cube. Season with salt and pepper and bring to a gentle simmer.
- Cook for 30 minutes, or until thick. Stir occasionally at the beginning and more regularly towards the end of the cooking time so that it doesn’t stick. Add a little extra water if necessary; it should look nice and saucy, but thick enough to support the weight of the potatoes. Adjust the seasoning to taste, making sure you are generous with the black pepper.
- While the vegetables are simmering, make the mash. Put the potatoes in a large saucepan and cover with cold water. Bring to the boil, then reduce the heat slightly and cook for 15 minutes or until very soft.
- Preheat the oven to 200C/180C Fan/Gas 6.
- Drain the potatoes in a colander then return to the pan and mash with the almond milk, oil and nutritional yeast. Add a little more milk if necessary, so that the potatoes are really light and fluffy. Season with salt and pepper.
- Pour the lentil mixture carefully into a 2.5 litre/4½ pints ovenproof dish – a lasagne dish is ideal. Spoon the potatoes gently onto the filling and fluff up the surface with the back of a spoon.
- Bake for 30 minutes, or until pale golden-brown and bubbling. If the topping doesn’t go brown enough, pop under a hot grill for a couple of minutes. Serve hot.