Preheat oven to 350°F and grease a mini donut pan.

Stir together flour, cocoa powder, baking powder, and salt in a medium bowl.

In a large bowl, mix together mashed avocado, melted chocolate, vanilla, and sugar until smooth.

Stir dry ingredients and milk into avocado mixture until well incorporated.

Put about 2 tablespoons of batter into each mini donut well and smooth tops.

Bake for 10 minutes.

Let cool in pan 1 minute, then remove donuts to a cooling rack. Clean pan of any stuck bits, grease again, and bake with remaining batter.

If desired, when donuts are cooled, fill a paper or zip-top bag with powdered sugar, add donuts, and shake to coat.