Preheat oven to 350 degrees F. Prepare a piping bag fitted with a small round tip. Lightly grease mini donut pan with cooking spray ( Pam, Baker’s Joy) or use a non stick donut pan.
Sift together flour, cocoa powder, baking powder, salt and espresso powder. Place into a medium size bowl and whisk in sugar. Set aside.
Whisk together melted butter, egg, milk and vanilla paste.
Add wet ingredients to bowl of dry ingredients. Mix well until combined and there are no dry streaks of flour left.
Fill prepared piping bag with batter. Pipe batter into prepared donut pans, filling mold a little over half full. Bake 8-10 minutes. Let cool in pan for 2 minutes before unmolding. Let donuts cool on rack before frosting or decorating.