For the Donuts! 🍩 In a bowl, sift together the cake flour, baking powder, salt, and nutmeg.
In the bowl of a stand mixer fitted with a paddle attachment, beat the butter and sugar together until sandy. Add the egg yolks and mix until light and thick. Add the dry ingredients to the mixing bowl in 3 additions, alternating with the sour cream, ending with the flour. The dough will be sticky. Cover with plastic wrap and chill for 1 hour.

On a floured surface, roll out the dough to about 1/2 inch thickness. Use biscuit cutters to cut out as many donuts as possible, dipping the cutters into flour will to prevent sticking. You should get about 12 doughnuts and holes.
Pour 2 inches of canola oil into a heavy bottomed pot with a deep-fry thermometer attached. Heat to 325°F. Fry the doughnuts a few at a time, fry on each side about 2 minutes, don’t let them burn. Let drain.

For the glaze! 🥯Whisk all ingredients in a bowl until smooth. Dip each doughnut into the glaze. Place on a wire rack, Let sit until glaze is set.