Heat the fat: Warm 1 tablespoon butter or olive oil in a large skillet over medium heat.
Add 2 teaspoons freshly ground black pepper and 1 tablespoon nutritional yeast (if using) and sauté, swirling, for 45–60 seconds until fragrant.
Add the drained and rinsed butter beans and 1 cup low-sodium imitation chicken broth (or water); stir to combine.
Bring to a simmer over medium heat and cook, stirring occasionally, 7–9 minutes until the liquid is reduced by about half.
Reduce heat to low and add 2 ounces shredded Parmesan; gently fold until the cheese melts and the sauce thickens, about 1–2 minutes.
Adjust consistency by adding warm water 2 tablespoons at a time if the sauce is too thick; season with salt and more pepper to taste.
Serve warm, garnished with chopped parsley if desired.
