Special equipment: a doughnut cutter
In a medium bowl, sift together the cake flour, all-purpose flour, milk powder, baking powder, salt and mace. Split the vanilla beans down the center with a paring knife and scrape out the seeds. Place the seeds in the bowl with the dry ingredients.
Whisk, either by hand or in a mixer, the sugar and eggs until pale and fluffy, 1 to 2 minutes. Combine the dry ingredients and melted butter with the egg mixture and mix the batter until very smooth. Cover the bowl with plastic wrap and refrigerate for at least 2 hours and up to overnight.
Place a generous amount of flour on the countertop and roll out the chilled dough to 1/2-inch thick. Using a doughnut cutter, punch out the doughnuts.
Place a deep-fry thermometer in a medium saucepan. Pour the oil into the pan until it is about 2-inches deep. Heat the oil over medium-low heat until the deep-fry thermometer reaches 360 degrees F.
When hot, fry 2 or 3 doughnuts at a time. After 30 seconds flip the doughnuts using a wooden spoon (be careful not to splash). After 1 minute, flip them again and continue to fry until golden brown, 1 minute more. Flipping them twice creates the signature cracked look of the old-fashioned doughnuts. Carefully remove the doughnuts, drain, and then rest on paper towels.
For the icing: First make the simple syrup by bringing 100 grams water and the sugar to a boil, and cook until the sugar dissolves and the mixture is clear, 30 seconds. At this point the syrup can be cooled and stored or used immediately.
Chop the chocolate into small pieces and place in a medium bowl. Bring the cream and simple syrup to a simmer and pour over the chopped chocolate. Mix with a rubber spatula or immersion blender until it is very smooth and shiny. Allow the mixture to cool to 130 degrees F, then whisk in the confectioners' sugar until smooth again. Hold the icing warm, or gently reheat to 130 degrees F over a bain marie (water bath) or in the microwave when needed.
Once the doughnuts have cooled enough to handle, dip one side into the warm chocolate icing. Allow the icing to set and enjoy!
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.