Ingredients

• 5 pounds medium russet potatoes, peeled and cut into 1-inch chunks
• 12 tablespoons (1 1/2 sticks) unsalted butter, cut into 1/2-inch cubes
• Kosher salt and freshly ground black pepper
• 1 cup sour cream
• 1 1/2 to 2 cups milk, warm
• 2 tablespoons sliced chives

Instructions

1. Toss the potatoes, butter, 1 tablespoon salt and 1/2 teaspoon pepper together in a 6-quart slow cooker. Add 1 cup of water, then cover and cook on high until the potatoes are tender, about 4 hours. (The potatoes might have browned lightly in spots but that is okay.)
2. Remove the lid and add the sour cream and 1 1/2 cups warm milk to the potatoes. Use a potato masher to smash the potatoes until they are mostly smooth. If the potatoes need to be thinned out, stir in the remaining 1/2 cup warm milk. Season to taste with additional salt and pepper. Garnish with chives.