Peel and cut the potatoes into 1-inch pieces and place them in a large pot. Cover the potatoes with cold water and place on the stovetop over high heat. Bring to a boil and cook until the potatoes are fork tender but not yet flaking.
While the potatoes cook, melt the butter, heavy cream, and blue cheese together in a small saucepan. It doesn't need to boil, just get hot.
Strain the potatoes and transfer them to a mixing bowl. Mash them on the lowest speed of an electric mixer or by hand with a potato masher or ricer. Add in the hot blue cheese mixture and stir until combined. Season with salt and pepper and serve with extra blue cheese and melted butter on top.
Notes
These blue cheese mashed potatoes will stay fresh in the fridge for up to 4 days.
To reheat them, place the potatoes into an oven safe container. Spread out 3-4 tablespoons of butter along the top of the potatoes, cover them with foil and bake at 350°F for 20 minutes or until heated through. Remember, the deeper your pan, the longer it takes to reheat.