Creamy Make-Ahead Mashed Potatoes

Butter a 9x13 baking dish. Set aside.
Peel the potatoes and cut them into large cubes. Add the potatoes to a large pot and fill the pot with water.
Bring the water to a boil over high heat. Once boiling, reduce the temperature to medium heat, and cook for 20 minutes. The size of your potatoes will determine the cook time. Larger potatoes may take longer. The potatoes are done when they are easily pierced with a fork.
Drain the potatoes in a colander, then place back on the stove for one minute to remove excess moisture.
Mash the potatoes using a potato masher or ricer.
Add all of the ingredients and fold into the potatoes. If you prefer lumpy mashed potatoes, skip to the next step. For smooth mashed potatoes: beat on high speed for 1 to 2 minutes using a hand mixer, until the potatoes are light and fluffy.
Spread the potatoes evenly in the prepared baking dish. Press a layer of plastic wrap against the potatoes and then cover them with aluminum foil. Store in the refrigerator for up to 3 days.
When ready to serve, preheat the oven to 350°F.
Remove the plastic wrap, but place the foil back over the top of the casserole dish. Bake for 35 to 45 minutes, until the potatoes are heated through. Top with additional butter and chives, if desired.