01 -
In a bowl, sift together the cake flour, baking powder, salt, and nutmeg.
02 -
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.
03 -
Add the dry ingredients to the mixer in 3 additions, alternating with the sour cream, ending with the flour. Mix on low speed for 30 seconds or until smooth but slightly sticky. If the dough is too sticky, add extra flour one tablespoon at a time.
04 -
Cover the dough with plastic wrap and chill for 1 hour, or until firm.
05 -
On a floured surface, roll out the dough to about 1/2 inch thickness. Use a doughnut cutter or two differently sized biscuit cutters to cut out 12 doughnuts and holes. Return the dough to the refrigerator if it becomes sticky or greasy.
06 -
Pour 2 inches of canola oil into a heavy-bottomed pot with a deep-fry thermometer attached. Heat to 325°F.
07 -
Fry the doughnuts a few at a time, being careful not to overcrowd the pot. Cook for about 2 minutes per side. Adjust the stove heat to maintain the oil temperature. Drain on a paper bag to remove excess grease.
08 -
In a bowl, whisk together powdered sugar, corn syrup, salt, vanilla extract, and hot water until smooth.
09 -
Immerse each doughnut into the glaze. Place on a wire rack above a sheet pan to catch the excess glaze. Let sit for 20 minutes until the glaze sets. Serve immediately or store in an airtight container.