Heat oven to 425°F.
Bring a large pot of water to a boil. Add sweet potatoes, 1 tablespoon of Kosher salt, and ½ teaspoon of baking soda. Cook for 12–13 minutes, until the potatoes are fully cooked and very tender. Drain water.
Return potatoes to pot and toss with olive oil. Using a wooden spoon or spatula, stir the potatoes, until a mashed potato–like paste has collected around each potato. (This will crisp up in baking.) Spread the potatoes on 2 sheet pans, making sure not to crowd them, then roast for 25 minutes.
Remove pans from the oven, gently toss the potatoes, then return to the oven for another 10–15 minutes until they are deeply browned and crisped. Remove from the oven and rest until you are ready to serve.
Meanwhile, stir together the Momofuku Sweet & Spicy Korean BBQ Sauce and the Greek yogurt until smooth.
When you are ready to serve, toss cooked potatoes (they can still be warm) with the dressing. Top with chopped cilantro.
