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.
Whisk a ladleful of the pasta cooking water into the egg mixture, then slowly pour it into the ’nduja and pasta mixture, stirring until the cheese has melted and formed a glossy sauce ...