Preheat your oven to 350°F (175°C) and grease a mini donut pan.
In a mixing bowl, whisk together the flour, sugar, baking powder, baking soda, and salt.
In another bowl, combine buttermilk, egg, melted butter, and vanilla extract.
Pour the wet ingredients into the dry ingredients and mix until just combined.
Transfer the batter to a piping bag or a zip-top bag with the corner cut off.
Pipe the batter into each donut mold, filling them about halfway.
Bake for 8-10 minutes until the donuts are golden and a toothpick comes out clean.
Allow the donuts to cool for a few minutes before removing them from the pan.
Dip the tops in melted chocolate or sprinkle with powdered sugar.
Let the toppings set before serving. Enjoy your mini donuts!