Cook the lentils in water according to the packet instructions until soft, then drain and leave to cool. Roughly mash the lentils. Heat the oil, sauté the onion, garlic, carrots and thyme for approx. 3 mins. Add the mushrooms and cook for a further 2 mins. Place in a bowl, add the tomato puree, walnuts, chestnuts, linseed and lentils, season. Transfer to the loaf tin, press down gently.
Approx. 25 mins. in the centre of an oven preheated to 180°C.
Heat the oil, sauté the onion, garlic and thyme. Pour in the balsamic and water, add the porcini mushrooms and tomato puree, bring to the boil. Simmer the sauce over a low heat for approx. 20 mins. Puree the sauce, add the maple syrup, season. Serve the sauce with the lentil and chestnut roast.