In a large mixing bowl, beat together the melted butter and sugar until they are mixed well. Add the egg yolks and continue mixing until they are well combined and the mixture is smooth. Place the sour cream and vanilla extract in the bowl and again mix until the mixture is smooth and cohesive.

In a separate, smaller bowl, mix together the dry ingredients- cake flour, Dutch-process cocoa powder, baking powder and salt.

Add the dry ingredients to the wet and mix until they are well combined. The dough should be fairly stiff, but still sticky and soft.

Place the donut batter on a sheet of plastic wrap and flatten it into a disc about 2″ thick. Wrap it well and refrigerate for at least an hours or up to 2 days.

Remove the chocolate donut dough from the refrigerator and place it on a floured surface. Roll it out to between 1/4″-3/8″ thick, then cut as many donuts as possible from the dough. Set the cut donuts aside.

Brush any excess flour off of the remaining dough and press it into a ball. Repeat the rolling and cutting process until you’ve used all of the dough.

Frying the Chocolate Donuts

Set out all of your tools before you begin heating the oil. You’ll need a slotted or holed metal spoon, a frying thermometer, a 6 quart pot, and a cooling rack with a baking sheet underneath it to set the fried donuts on.

Place about 2 quarts of oil in a 5 or 6 quart pot.

Using a frying thermometer to monitor the oil temperature, heat it to between 350° and 375°.

Once your oil has reached the correct temperature, turn it down to medium-low to make sure it doesn’t over-heat. You will need to adjust and figure out the best setting for your burners.

Add 2-3 donuts at a time and fry them for 1 minute and 30 seconds.

Flip the donuts and fry them on the other side for another minute and a half, then remove them from the oil to the cooling rack.

Repeat the frying process with the rest of the donuts, making sure to keep the oil between 350° and 375°.

Allow the donuts to cool, then glaze them.

Glazing the Donuts:

To make the glaze for the chocolate donuts, heat 1/4 cup of whole milk in a small saucepan until it’s steaming. Add 2 cups of sifted powdered sugar and 1 tsp. of vanilla extract to the milk and whisk them together until you have a smooth, runny glaze.

Dip one side of a donut in the glaze, then flip it over to coat the second side. Remove the donut from the glaze and allow the excess to drip back into the pan.

Set the donut back on the cooling rack and allow the glaze to cool. Repeat until all of the donuts are glazed.