Heat whey in a large pot over medium-high heat. Season with salt. When whey comes to a boil, drizzle in polenta and stir to prevent clumping until it starts to rehydrate, about 2 minutes. Turn heat to low and cover. Cook about 30 minutes, lifting lid every 5 minutes to stir, ensuring that polenta is not sticking to bottom of the pot. Remove from heat and add butter and a generous amount of black pepper, to taste. Serve as is, or top with a dollop of pesto and toasted nuts.