Prepare the potatoes: Peel (optional) and cut potatoes into even 1- to 1 1/2-inch chunks so they cook uniformly.

Salt the water: Place potatoes in a large pot and cover with cold water by about an inch. Add a teaspoon of kosher salt to the water.

Bring to a boil and simmer: Bring to a gentle boil, then reduce to a simmer. Cook until potatoes are fork-tender, about 12–15 minutes depending on size.

Meanwhile prepare the garlic: While potatoes cook, heat a small skillet over medium-low heat with a tablespoon of butter or oil and gently sauté minced or thinly sliced garlic until fragrant and soft (about 1–2 minutes). Alternatively, roast whole garlic cloves for a sweeter, milder flavor.

Warm the dairy: In a small saucepan or microwave-safe bowl, warm the butter and milk together until the butter is melted and the mixture is warm but not boiling. This prevents cooling the potatoes when mixed.

Drain and return potatoes: Drain potatoes thoroughly and return them to the warm pot. Let them sit for a minute to allow excess moisture to evaporate.

Mash: Mash the potatoes using a potato masher, ricer, or hand mixer on low speed until mostly smooth. For the creamiest texture, a ricer or food mill works best.

Add dairy and garlic: Stir in the warm butter and milk mixture, the sour cream, and the sautéed or roasted garlic. Mix until fully combined and creamy. Adjust the amount of milk or sour cream to reach your desired consistency.

Season and finish: Taste and add additional salt and pepper as needed. Fold in chopped chives and, if desired, a pat of butter on top for presentation.

Serve: Transfer to a warmed serving bowl and serve immediately while hot, or keep covered in a low oven (200°F/95°C) for up to 20–30 minutes.