Preheat your oven to 350°F (175°C) and grease the donut pan.
In a bowl, whisk together the dry ingredients: flour, cocoa powder, sugar, baking powder, baking soda, and salt.
In another bowl, combine the wet ingredients: eggs, buttermilk, oil, and vanilla extract.
Pour the wet mixture into the dry ingredients and mix until just combined.
Spoon the batter into the prepared donut pan, filling each cavity about two-thirds full.
Bake for 10-12 minutes or until a toothpick inserted comes out clean.
Let the donuts cool in the pan for 5 minutes before transferring them to a wire rack.
Once completely cool, dip them in chocolate glaze and add toppings if desired.