Make-Ahead Slow Cooker Mashed Potatoes

Place potatoes into a large pot, cover with water, and bring to a boil over high heat. Reduce the heat to medium-low and simmer until tender, 20 to 25 minutes. Drain; return potatoes to the pot and stir gently over medium heat until dry, 1 to 2 minutes.

Mash potatoes with a hand mixer until smooth. Stir in cream cheese, half-and-half, chives, egg whites, onion powder, salt, and pepper until well blended.

Spray a slow cooker insert with nonstick spray and add mashed potatoes. Cut 1/2 cup butter into 8 pieces and scatter over the top of potatoes. Allow potatoes to cool, then cover with lid and store in the refrigerator overnight or until ready to reheat.

Remove potatoes from the refrigerator and let them come to room temperature, about 3 1/2 hours.

Place a towel under the lid to absorb condensation. Cook on Low, stirring once or twice, 2 1/2 hours. Stir in remaining 1/4 cup butter, 1 tablespoon at a time; then cook for another 30 minutes.