Pre-heat oven to 350˚ F. Coat your mini donut pans with baking spray.
Sift together flour, baking powder, baking soda, and salt. Set aside.
Whisk the softened butter and sugar in the stand mixer. Then, add egg, milk, and vanilla and mix again, be sure to scrape the sides. Don't worry if the mixture is lumpy.
Add the flour mixture into the wet ingredients. Scrape the sides.
Place a no. 12 piping tip into a piping bag and then fill the bag with the batter. If you don't have these items then, put your batter in a zip lock bag and cut a small hole in one of the corners.
Pipe the batter into the mini donut pan. One swirl per donut is enough. Don't overfill.
Place in the oven and bake for 10-13 minutes or until the donuts are a bit golden.
Remove from the oven and then dip each donut into the colorful sprinkling sugar.