Prep the potatoes: Peel and cut the potatoes into even chunks so they cook at the same rate. Rinse briefly under cold water to remove surface starch.

Start in cold water: Place the potatoes in a large pot and cover with cold water by about an inch. Add 1 tablespoon salt. Starting cold helps the potatoes cook evenly.

Boil until tender: Bring to a gentle boil and cook 12–18 minutes, until a fork slides in easily with no resistance. Don’t overcook or they’ll get waterlogged.

Warm the dairy: While the potatoes cook, melt the butter in a small saucepan. Add the milk (and sour cream or heavy cream if using) and heat gently until warm. Warm dairy blends in better and keeps the texture smooth.

Drain well and dry: Drain the potatoes thoroughly. Return them to the hot pot and set over low heat for 1–2 minutes, shaking the pot, to steam off excess moisture.

Mash while hot: Use a potato masher, ricer, or food mill to mash the potatoes. For the smoothest texture, a ricer or food mill is best.

Add butter first: Pour in the melted butter and stir gently with a spatula until absorbed. Butter coats the starches and helps prevent gumminess.

Add warm milk gradually: Stir in the warm milk a little at a time until you reach your desired creaminess. You may not need all of it.

Season: Add salt and pepper. Taste and adjust. If you want richer flavor, stir in another tablespoon of butter.

Finish and serve: Transfer to a warm bowl, dot with a little butter, and sprinkle with chopped chives or parsley if you like. Serve right away.