Prep: 7 minutes; Cook: 30 minutes. You can get a head start on this sure-hit dish by cooking and refrigerating the potatoes a day before your meal.
Boil potatoes and garlic cloves in lightly salted water until tender, about 30 minutes. Drain and cover potatoes with a towel to keep warm.
Bring the 1% milk and butter to a boil and cover to keep warm.
Use a ricer to rice the potatoes into a large bowl. The potatoes may also be mashed with a large fork, but they might not be as smooth.
Gradually add the hot milk and butter, then add the buttermilk until you get the consistency of thick mashed potatoes (you may not need to use all of the buttermilk). Season with salt to taste. Coat a 9- x 13-inch baking dish with cooking spray, place the potatoes in the dish, and top with freshly chopped chives. Serve immediately, or rewarm in the oven before serving.