If you don't already have a stick of frozen butter in your freezer, place a stick in there now or cut off 1 tablespoon and put it in a freezer-safe bowl and place into the freezer.
Preheat your oven to 400°
Using your favorite non-stick cooking spray, lightly spray your donut pan.
In a large bowl, add the Bisquick, the white granulated sugar, and the ground cinnamon. Using a whisk, whisk the dry ingredients together and set aside.
In a small bowl, whip the egg using a fork or a small whisk. Then add into the dry ingredients.
Then into the large bowl, add the vanilla extract and milk.
Using a wooden spoon, stir the ingredients together until the mixture is smooth. If you think it looks a bit dry, add in some more milk, 1 tablespoon at a time.
Next, grate the frozen butter onto the top of the batter and then stir.
Fill each donut mold 2/3rds of the way full.
Bake for 6 to 8 minutes until they are starting to brown on the sides.
Let cool then dip in a cinnamon-sugar mixture or your favorite chocolate glaze. Then serve.