How to Make It
In a medium saucepan, cover the potatoes with 2 inches of water. Add 1 teaspoon of sea salt and bring to a boil, then simmer over moderate heat until the potatoes are tender when pierced, about 30 minutes. Drain well, then return the potatoes to the hot saucepan and mash with a potato masher.
Meanwhile, in a small saucepan, melt the butter. Remove from the heat and stir in the buttermilk and baking soda; the mixture will foam up. Stir the buttermilk mixture into the mashed potatoes and season with sea salt and pepper. Scrape the potatoes into a serving bowl and garnish with chives. Serve warm.