Peel all of the potatoes and evenly cut into large cubes.
Add the potatoes to a large pot and add cold water until potatoes are covered with 2–3 inches of water.
Add in a 5-finger pinch of salt and the garlic. Bring to a boil, then lower to a simmer and cook until the potatoes are fork tender.
In the meantime, bring a small pot to the stove. Add the heavy cream, thyme, and lemon peels (use a potato peeler to thinly peel the lemon and cut out as much white pith as possible). Keep warm over low heat.
Once the potatoes are fork tender, drain. Briefly return to the pot to remove excess moisture.
Pass all of the potatoes through a ricer or food mill for the smoothest texture (hand mashing also works, but won’t produce as smooth of a texture).
Pour in half the heavy cream and stir well. Slowly incorporate the rest until you achieve the desired consistency. Season with salt and pepper to taste.
Add in the cold butter and stir to incorporate (this adds a beautiful shiny finish).
Garnish with thinly sliced butter and fresh thyme or thinly sliced chives.
