Preheat the oven to 450 degree F. Place the potatoes, ¾ vinegar, and the salt in a large pot. Add water to cover by 1 inch. Bring to a boil, then reduce the heat to a simmer. Simmer 15 minutes, until the potatoes are fork tender. Drain the potatoes and transfer to a rimmed baking sheet, let cool slightly.
Place another rimmed baking sheet on top of the potatoes, then push down firmly to smash potatoes. Alternately, use the bottom of a mug to smash each one individually. Toss the potatoes with olive oil, onion powder, garlic, and season with salt and pepper, lightly breaking the potatoes as you toss. Transfer to the oven and roast the potatoes until light golden brown, 25-30 minutes. Remove from the oven, sprinkle on the cheese, toss, and return to the oven for another 10 minutes, until the potatoes are crisp and golden brown.
Toss the potatoes with the remaining 2 tablespoons vinegar, herbs, and chives.
Spoon the yogurt onto a serving plate and then add the potatoes. Sprinkle with fresh herbs and flaky salt. Enjoy!
