- 5 pounds russet potatoes, peeled, sliced into 3/4-inch thick rounds, and rinsed thoroughly
- 2 1/2 cups whole milk, warmed
- 1 cup sour cream
- 8 tablespoons unsalted butter, melted
- 2 1/2 teaspoons Dijon mustard
- 1 large garlic clove, minced (1 teaspoon)
- 1/8 teaspoon cayenne
- salt and pepper
- 8 ounces extra sharp cheddar cheese, shredded (2 cups)
- 3/4 cup Italian bread crumbs
- 2 tablespoons unsalted butter, melted
- Place potatoes in large Dutch oven or pot and cover by 1 inch of water. Bring to a boil over high heat, then reduce to a simmer and cook until the potatoes are tender, about 15 minutes.
- Drain the potatoes in a colander. Set a food mill or ricer over the now empty, but still warm, pot. Working in batches, process the potatoes into the pot. Stir in the milk, sour cream, butter, Dijon, garlic, and cayenne until combined. Season with salt and pepper to taste.
- Spread the potato mixture into a 9x13 baking dish. Sprinkle the cheese evenly over the top. Stir together the bread crumbs and melted butter until uniform, then sprinkle over the top of the cheese.
- Cover the dish tightly with plastic wrap and refrigerate for up to 2 days.
- Preheat oven to 350. Remove plastic wrap and cover the dish tightly with foil. Bake for 20 minutes. Remove foil and continue to bake until heated through and crumbs are crisp, 20-30 minutes longer.
To Serve Right Away:
- Bake the mashed potatoes in 350-degree oven, uncovered, until hot throughout, 25-30 minutes.