Cut potatoes into 2-inch pieces. Bring a large pot of salted water to boil. Cook potatoes until fork-tender. Drain well; then place them back in the warm pot. Swirl the cooked potatoes around the pot, until a thin film of starch appears.
In a small pan, heat cream and butter until butter melts. Pass potatoes through a ricer or food mill, or break up with a potato masher until smooth. Add heated cream and butter; mix well. Season with salt and pepper to taste.