Place the 3 lb Yukon Gold potatoes peeled and cut into 1½-inch chunks chunks and smashed 6 cloves garlic peeled and smashed cloves in a large pot. Cover with cold water by at least 1 inch and add a generous pinch of kosher salt (about 1 tbsp). Starting in cold water ensures the potatoes cook evenly all the way through.

Bring the pot to a boil over high heat, then reduce to a steady simmer. Cook until the 3 lb Yukon Gold potatoes peeled and cut into 1½-inch chunks are completely tender and a fork slides in with no resistance, about 18–22 minutes.

While the potatoes cook, warm the ¾ cup heavy cream and ¼ cup whole milk together in a small saucepan over low heat, or microwave in a measuring cups for about 60 seconds.

Drain the 3 lb Yukon Gold potatoes peeled and cut into 1½-inch chunks and 6 cloves garlic peeled and smashed thoroughly in a colander, then return them to the hot pot. Shake the pot over low heat for 1–2 minutes to evaporate any remaining moisture.

Use a potato masher or ricer to mash the 3 lb Yukon Gold potatoes peeled and cut into 1½-inch chunks and 6 cloves garlic peeled and smashed together until smooth. If using a ricer, pass the 6 cloves garlic peeled and smashed through separately or mash it first with a fork. Avoid using an electric mixer or blender — over-working releases too much starch and makes the potatoes gluey.

Add the room-temperature 6 tbsp unsalted butter cut into pieces pieces and stir them in with a wooden spoon or spatula until fully melted and incorporated.

Pour in the warm ¾ cup heavy cream and ¼ cup whole milk gradually, stirring gently after each addition, until the potatoes reach your desired consistency. Add a splash more warm ¼ cup whole milk if you prefer them looser. Season with 1½ teaspoons kosher salt and freshly ground ½ tsp black pepper freshly ground, then taste and adjust.

Transfer to a warm serving mixing bowl. If desired, make a small well in the center and add a pat of unsalted butter cut into pieces. Garnish with fresh fresh chives thinly sliced and an extra crack of black pepper freshly ground. Serve immediately.