Cook uncovered until a fork passes easily all the way through a potato chunk. Quickly drain and return the hot potatoes to the hot pot. This helps the potatoes dry off a little. Add the salt, ½ t. pepper, all the butter, and ½ cup of buttermilk. Mash with the potato masher until most of the lumps are gone. If the potatoes seem dry, and some more of the buttermilk and mash some more. Taste for salt and pepper, and correct if necessary. It will likely need more of both. Don’t over mix the potatoes or they will get gluey.