In a large mixing bowl, whisk together flour, cocoa powder, sugar, baking powder, soda and salt.
In another bowl, whisk together buttermilk, egg, oil and vanilla.
Add wet ingredients to dry ingredients and whisk until smooth.
Add chocolate chips and stir.
Divide the batter evenly in the donut pan.
Bake donuts for 8 to 10 minutes. Cool in pan for 10 minutes, then transfer onto a cooling rack.
To make the glaze:
In a medium mixing bowl, whisk together peanut butter and melted butter.
Add sifted confectioners sugar and vanilla and whisk until smooth. It may look clumpy at first but keep whisking, it will become smooth. It will be thick but easily spreadable. You can warm it up in a microwave to make it more drizzling consistency.