https://cooking.nytimes.com/recipes/1018430-aligot-mashed-potatoes-with-cheese
Simmer the potatoes in water until very tender to the point of a knife, about 15 to 20 minutes. Drain potatoes, and tip out any remaining water from the pot. Push the hot potatoes through a ricer back into the pot. Over low heat, use a heatproof spatula to move the potatoes around the pot for a minute so that any excess water can evaporate.
Add butter to the potatoes, half at a time, stirring until completely incorporated. Add hot cream, half at a time, stirring until incorporated. Add cheese a little bit at a time, stirring vigorously, until all the cheese is evenly melted and the spoon makes cheesy strings as you pull it away from the potatoes. If necessary, turn the heat up a little. Taste, and season with salt. Serve.