In a large bowl, sift together flour, cocoa powder, baking powder, baking soda and salt.

In a smaller bowl, whisk together buttermilk, eggs, sugar, melted butter and vanilla extract. Add the wet ingredients to the dry all at once. Stir with a spoon/rubber spatula until the dough comes together.

Line a baking sheet with parchment paper. Lightly dust some flour on to your hands; this will help keep the dough from sticking. Roll dough into balls just smaller than a golf ball in size and then place them on to the parchment lined baking sheet.

Fill a large, heavy-bottomed skillet about 2/3 of the way up with vegetable oil. Heat over medium/high heat. Once it reaches 350 degrees F, add 2-3 donut holes at a time, frying for 2-3 minutes. Use a slotted spoon to turn the holes a few times so they fry evenly. Place fried doughnut holes on wire rack to cool and drain. Continue this process until all doughnut holes have been fried.

To make the glaze, combine the powdered sugar, milk, and vanilla extract in a large bowl. Whisk to combine. Dip each doughnut hole into the glaze and then set each on a wire rack to set up. While the doughnut holes are still wet, sprinkle with sprinkles, if using.