Chocolate Cake Doughnuts

Portioned donuts for chocolate cake are even tastier if they are drizzled with mocha icing, and sprinkled with coconut chips, chocolate, nuts or sugar sprinkles on top.
In a large bowl, combine the flour, cocoa, baking powder, and salt. In a small bowl, whisk together the eggs, sugar, buttermilk and melted butter until smooth. Mix with the dry ingredients until smooth. Refrigerate until completely cooled, at least 1 hour or up to 3 hours.Place the dough on a generously floured surface. With floured hands, roll out the dough about 1/2 inch thick. Use a 3-inch donut mold to cut out the donuts. Dip the dough pieces together and cut again. (Alternately shape the dough into bundles about 5 inches long and 1/2 inch thick; connect the ends of the bundle to form doughnuts.) Place the doughnuts on a well-floured baking sheet.Meanwhile, fill the electric fryer to fill level, or pour about 4 inches of oil into a 5-to 6-quart skillet; preheat to 375 degrees (see "Frying Properly" below). Spread one doughnut at a time on a wide spatula and gently dip in the oil, frying up to three at a time. Cook, turning once, until fluffy and tender, just 3-4 minutes (to check the time, cut the first doughnut for the dough). Use a slotted spoon to transfer the doughnuts to paper towels to dry. Repeat to brown the remaining donuts.When the doughnuts are cool enough to handle, dip the top half of each doughnut in the warm mocha glaze and place on a plate. Let stand until the glaze is set, about 5 minutes.Mocha glaze. In a heatproof bowl, combine 6 ounces of crushed semisweet chocolate, 1/2 cup whipped cream, 1 tablespoon butter, 2 teaspoons corn syrup, and 1 teaspoon instant espresso powder. Bring a few inches of water to a boil in a saucepan; remove from heat. Place the bowl on the water and let it stand, stirring occasionally, until smooth, about 10 minutes.