Put the silken tofu and soy sauce in a tall jug and add 3 tablespoons of the reserved pasta water. Use a stick blender to blend to a smooth sauce, then pour into the pan with the mushroom mixture.
When ready, serve the Bolognese sauce with freshly cooked spaghetti, some grated cheese and basil, if you like. You can use any mushrooms you like for this Bolognese, but small chestnut mushrooms ...