Mashed Potato Croquettes

Mix 2 large egg yolks, 2 cups cold mashed potatoes, 1/2 cup grated Parmesan, 2 tablespoons chopped fresh chives, and 1 tablespoon all-purpose flour in a medium bowl. Roll into walnut-size balls; chill until cold, at least 2 hours. Beat 4 large eggs in a bowl; place 2 cups breadcrumbs in another bowl. Pour vegetable oil into a medium skillet to measure 1/2" (about 2 cups) and heat over medium-high until a pinch of breadcrumbs bubbles immediately when added. Dip potato balls in egg, then roll in breadcrumbs. Working in batches, fry, turning often, until golden brown and crisp, 3 –4 minutes. Drain on paper towels.