Place the peeled and quartered potatoes into a large pot, covering them with cold water. Add a generous amount of salt to the water. Bring the pot to a boil over high heat, then reduce the heat to medium. Allow the potatoes to gently simmer until they are completely tender, which should take around 30 minutes when tested with a knife.
Thoroughly drain the potatoes and return them to the pot. Place the pot back on low heat for about 2 minutes, letting any remaining moisture evaporate. Mash the potatoes until smooth using a potato masher.
Gradually fold in the cubed butter with a spatula until it has melted completely into the potatoes. Then, incorporate the warmed cream, stirring until the mixture is creamy and smooth. Adjust seasoning with salt and freshly ground black pepper to taste before serving.