Some may balk at this version of Bolognese, the classic Italian ragù, because it bypasses the meat and dairy that are traditionally integral to the dish. But this recipe is equally rich, robust and complex, owing to seared mushrooms and toasted walnuts, which are bolstered by balsamic vinegar, tomato paste, soy sauce and Marmite. A popular British sandwich spread made from concentrated yeast extract, Marmite brings salty, bitter notes to the sauce, but you can substitute a vegetable bouillon…
