Scrub potatoes under cold running water. Pat completely dry with a kitchen towel. Pierce each potato 8–10 times all over with a fork. Rub each potato with a light coat of olive oil and a generous sprinkle of kosher salt.

Place potatoes in a single layer in the air fryer basket. Air fry at 400°F for 30–40 minutes, flipping once at the halfway mark. Start checking at 30 minutes — a paring knife inserted into the thickest part should slide in with zero resistance.

While the potatoes finish, combine butter, cream, and milk in a small saucepan over low heat (or microwave) until the butter is melted and the mixture is steaming hot. Do not add cold dairy to the mash.

Let potatoes rest 5 minutes. Cut in half lengthwise and scoop the flesh into a large bowl, or peel the skin off by hand (it should come away easily). Discard skins.

Use a potato masher or potato ricer to mash until no large lumps remain. Do not use a hand mixer or blender — this over-works the starch and creates a gluey texture.

Pour the warm butter-cream mixture over the mashed potatoes gradually, stirring with a wooden spoon or rubber spatula between additions. Add only as much as you need to reach your preferred consistency.

Season generously with kosher salt and pepper. Taste and adjust. Transfer to a serving bowl, top with a pat of cold butter and fresh chives, and serve immediately.