Ingredients 4 large russet potatoes (about 1 pound each) 2 teaspoons olive oil, plus more for the pan 3/4 cup half-and-half 1/2 cup sour cream, plus more for serving 1 1/2 cups shredded Irish Cheddar cheese or your favorite Cheddar (about 7 ounces) 1/4 cup thinly sliced scallions, white and green parts (about 2 scallions) 2 tablespoons unsalted butter, melted…