Put the quartered Russet potato into a pot and cover it with water. Bring the pot to a boil over high heat and continue to boil until the potato is soft, about 10 minutes. Reserve ½ cup of the cooking water then drain the potatoes.
Add the butter and milk to the potatoes and mash well.
Put the potato water into the bowl of your stand mixer or large mixing bowl and add the sugar. Let the water cool until it is lukewarm then add the active dry yeast. Let the yeast bloom for 5 minutes.
Add the mashed potatoes and eggs to the bowl and mix using a dough hook or a wooden spoon.
Add the flour and salt and continue to mix in your stand mixer for 2-3 minutes, or until the dough comes together into a ball. If you're mixing the dough by hand, turn it out onto your counter and kneed it for 5 minutes.
Transfer the dough to a lightly oiled bowl and cover tightly. Place the bowl in a warm (not hot) place for 1 hour, or until the dough has doubled in size.
Bake as pull apart potato buns
Divide the dough into 15 balls. Place each ball seam-side down in a lightly oiled baking dish. They will be quite close together. Cover the baking dish and let the buns rise for 45 minutes.
Preheat your oven to 350 degrees. Bake the buns for 30-35 minutes, or until they are golden on top and they reach an internal temperature of 200 degrees Fahrenheit.
Let the buns cool before removing them from the baking dish.
Bake as individual potato buns
Divide the dough into 16 balls. Place each ball seam-side down on a lightly oiled baking sheet, spaced 2-inches apart. Bake the buns for 20-25 minutes, or until they are golden on top and they reach an internal temperature of 200 degrees Fahrenheit.
Let them cool slightly before serving.
Honey Butter Buns
Melt the butter and honey in a small bowl. Once the buns have cooled, brush the tops of the buns with the honey butter then sprinkle with some flaky sea salt.
You can also use leftover mashed potatoes in this recipe, but you'll need to increase the flour. Start by adding 2 extra tablespoons of flour and add more if needed until the dough is thick and sticky. Ad instead of using potato cooking water, use warm tap water.