How to Make It
Bring potatoes and salted water to cover to a boil in a large saucepan over high; cook until tender, about 10 minutes. Drain. Spread potatoes on a rimmed baking sheet, and cool about 10 minutes.
Meanwhile, place garlic and ¼ cup of the olive oil in a large high-sided skillet over medium, and cook, stirring often, until garlic begins to sizzle and brown on all sides, about 5 minutes. Remove garlic, and, if desired, reserve and serve with potatoes. Remove and reserve about half of the garlic oil in skillet.
Heat remaining garlic oil in skillet over medium; add potatoes, in 2 batches, and cook until golden and crispy, about 5 minutes per side. Transfer to a platter, and repeat with remaining potatoes, adding reserved garlic oil as needed. Sprinkle potatoes with ½ teaspoon of the salt.
Whisk together sherry vinegar, mustard, sugar, pepper, and remaining 1 teaspoon salt in a small bowl. Whisk in remaining ¼ cup olive oil. Drizzle potatoes with vinaigrette, and sprinkle with oregano.