Make the "whey": Blend the silken tofu, cashews, lemon juice, vinegar, nutritional yeast, and salt until completely smooth and glossy. Taste it now — it should be distinctly tangy and salty on its own, since it's about to get diluted by a lot of bland tofu curd.
Crumble the curds: Pat the firm tofu dry. Crumble by hand or fork into small, uneven, curd-sized pieces — some pea-sized, some bigger. Don't overwork into a paste; texture contrast is the point.
Combine: Fold the blended mixture through the crumbled curds until evenly coated. Loosen with plant milk, a teaspoon at a time, if it looks dry.
Rest: Chill at least 30 minutes (ideally 2+ hours for more authentic tang) before eating. Taste again and adjust salt or lemon.