01 - Place the peeled and chunked potatoes in a large pot. Cover with cold salted water by at least 2 inches.
02 - Bring the water to a rolling boil, then reduce the heat to a gentle simmer. Cook uncovered for 15 to 20 minutes, or until the potatoes yield easily when pierced with a fork.
03 - Drain the potatoes thoroughly in a colander. Return them to the still-warm pot to allow any residual moisture to evaporate.
04 - Add the unsalted butter to the hot potatoes and let it sit for 1 to 2 minutes until fully melted.
05 - Using a potato masher or potato ricer, work the potatoes until completely smooth and free of lumps.
06 - Gradually fold in the warmed milk and heavy cream, stirring gently until the mixture becomes light and creamy.
07 - Season with salt and freshly ground black pepper to taste. Stir gently until fully incorporated and the texture is velvety smooth.
08 - Transfer to a serving bowl and serve immediately. Garnish with an extra pat of butter or freshly chopped chives if desired.