Preheat the oven to 350 °F (177 °C). Prepare your donut pans by spraying generously with non-stick spray.
In a large bowl, whisk together the flour, cocoa, brown sugar, baking soda, baking powder, and salt. Set this aside.
1 cup flour, ½ cup unsweetened cocoa powder, ½ cup brown sugar, ½ teaspoon baking soda, ½ teaspoon baking powder, ¼ teaspoon salt
In a medium bowl, whisk the 2 eggs. Whisk in the buttermilk, melted butter, and vanilla. When this is fully combined, add these wet ingredients to the bowl with the dry ingredients (flour mixture).
2 eggs, ¾ cup buttermilk, ¼ cup salted butter, 1 teaspoon vanilla
Stir just enough to combine.
Place the batter into a piping bag. Pipe it into the prepared donut pans, filling each one ⅔ of the way full.
Bake for 12-15 minutes. (They should spring back when pressed gently.)
Remove them from the pan and place them on a cooling rack.
While they are cooling you could make the glaze. Whisk together the confectioners’ sugar and cocoa. Then whisk in the milk and vanilla until smooth.