Total time: 1 hour /30 min. Yield: Makes 20 potato poppers Olive oil 20 round baby potatoes, 1 to 1 1/4 inch in diameter Kosher salt 1/4 cup sour cream or whole-milk Greek yogurt 1/4 cup (packed) finely grated sharp cheddar cheese 2 T. unsalted butter, softened 2 T. (packed) finely grated fresh horseradish 1 large garlic clove, grated 1/2 teaspoon freshly ground black pepper 1/4 cup (packed) finely grated Parmigiano-Reggiano cheese, or more as needed Fresh thyme leaves or Heat the oven to 400 degrees. Line a baking sheet with foil and lightly oil the foil.