Preheat your oven to 350 degrees
In a large bowl, whisk together 1 large egg plus 1 egg yolk, 2/3 cup of sour cream, 2 teaspoons of vanilla extract, 1/4 cup of whole milk, 4 tablespoons of melted butter and 2/3 cup of brown sugar
Place a mesh sifter over the bowl and add 1/2 teaspoon of salt, 1 teaspoon of espresso powder, 1/3 cup of cocoa powder, 1 teaspoon of baking powder, 1/4 teaspoon of baking soda and 1 1/2 cups of all purpose flour into the sifter
Sift the dry ingredients into the wet ingredients
Mix the ingredients until just combined
Grease your doughnut pan
Fill each cavity 2/3 of the way
Bake the doughnuts for 10-15 minutes (depending on the size of your doughnuts) or until they feel springy and set to a light touch
Transfer the baked doughnuts onto a cooling rackĀ