Add tofu and cashews to a strong blender. (I do it in batches as the blender is small and to help the cashews incorporate well with the rest). Blend until smooth. Then mix in miso, nutritional yeast, lemon, salt, and pepper.
Blend until smooth, scraping down sides. Add a tiny bit of water only if needed to help the blades move.
Taste and adjust seasoning. Stir in chopped chives.
(optional): You can eat it immediately but I recommend letting it chill in the fridge for 30–60 minutes to firm.