- Preheat the oven to 190ºC/375ºF/gas 5. In a blender, cover the porcini with 600ml of boiling water. Trim, wash and slice the leeks 2cm thick, then scrub the carrots, swede and celeriac and chop to roughly the same size. Drizzle 2 tablespoons of oil into a large casserole pan on a medium heat, strip in the rosemary, fry for 1 minute to crisp up, then remove to a plate with a slotted spoon. Add the cumin seeds and prepped veg to the flavoured oil, season with sea salt and black pepper, and cook for 30 minutes, stirring regularly.
- Meanwhile, peel and roughly chop the potatoes, cook in a pan of boiling salted water for 15 minutes, or until tender, then drain well. Mash with the butter and milk, and season to taste. Quarter the onion, add to the porcini in the blender along with the Marmite and tomato purée and whiz until smooth. Pour into the veg pan and cook for 20 minutes, or until dark and caramelized, stirring regularly and scraping up any sticky bits from the bottom of the pan.
- Tip the lentils (juices and all) into the veg pan, bring to the boil, then season to taste. Spoon over the mash, place on a tray, bake for 30 minutes, or until lightly golden and bubbling at the edges, then sprinkle over the crispy rosemary.
- Serve with simple steamed seasonal greens – it’s a winner!
Veg by Jamie Oliver is published by Penguin Random House © Jamie Oliver Enterprises Limited (2019 Veg). Photography: David Loftus. Veg (2019). Approved PR recipe. Simply Christmas (UK) – Sept 2019.