In a large, heavy bottom pot, ideally large enough to fit all your potatoes in a single layer, cover your potatoes with cold water. Bring to a boil over high heat, then lower your heat to medium. Allow your potatoes to cook for 20-30 minutes, or until you can pierce your potatoes with a pairing knife with zero resistance.
While your potatoes are cooking, bring your milk to a boil with your thyme, garlic and black peppercorns. As soon as it comes to a boil, turn off the heat and allow the aromatics to steep while the milk stays hot.
When your potatoes are done cooking, strain them, and let them sit in the strainer for 5-10 minutes to allow steam to be released. Once they are cool enough to touch, but still hot, peel the potatoes & discard the skins.
Press your potatoes through a potato ricer into a large bowl. Strain the aromatics out of your milk, and pour half of the milk into the riced potatoes. Fold the milk gently into the potatoes until incorporated. Then, pass your potatoes once more through a fine mesh strainer into a large pot (this step is optional, but does result in THE smoothest potatoes).
