Place potatoes in a saucepan of cold water and bring to the boil, season with salt. Simmer until tender. Drain and return potatoes to saucepan. Shake saucepan over low heat to remove any remaining moisture from potatoes
Mash potatoes using a potato masher. Add butter and mix vigorously with a wooden spoon until smooth
Add hot milk to potatoes and continue to stir until smooth and creamy.