Place the peeled and cubed potatoes in a large pot and cover with cold water by at least an inch. Add a generous handful of salt. Bring to a boil over high heat, then reduce to a simmer and cook for 15-20 minutes until the potatoes are very tender when pierced with a knife.

While the potatoes cook, combine the heavy cream, milk, and smashed garlic cloves in a small saucepan. Simmer gently on low heat for 5 minutes to infuse the garlic flavor, then remove the garlic cloves and keep the liquid warm.

Drain the potatoes in a colander. Immediately return the potatoes to the hot, empty pot and place it back on low heat. Gently shake the pot for 1-2 minutes to steam-dry the potatoes, removing excess moisture.

Pass the hot potatoes through a potato ricer or food mill back into the pot. Alternatively, use a hand masher, but do not use a food processor or blender.

Pour half of the warm cream mixture over the riced potatoes and gently fold it in with a spatula. Add the softened butter cubes.

Gradually add the remaining cream mixture until you reach your desired consistency. Be careful not to overwork the potatoes.

Season with salt and freshly ground black pepper. Transfer to a serving bowl and garnish with fresh chives and an extra pat of butter if desired.