Vegan mushroom bolognese

1) Wash and dry mushrooms then blitz in a food mixer until fine.
2) Fry the onions and garlic over a low heat in the olive oil for a few minutes to soften.
3) Add the mushrooms and stir to mix well.
4) Add the yeast flakes, oregano, miso paste and tomato puree. Stir to coat and allow to cook for a couple of minutes. Season to taste.
5) Add the leeks, lentils, balsamic vinegar and tinned tomatoes, bring to a simmer and cook over a low heat for 30 minutes stirring occasionally.
6) 20 minutes before the end of cooking, bring a big pan of salted water to the boil and add pasta of your choice and cook according to the packet instructions.
7) Drain and add the pasta to the sauce.
8) Stir to coat and serve immediately with some grated vegan cheese if desired.