Preheat the oven to 375 F, and position a rack in the center of the oven. Spray your doughnut pans with non-stick baking spray.This recipe makes enough batter for about 12-14 standard-sized donuts (around 3 inches) or 3 dozen mini donuts. If you don't have enough pans, let the batter rest at room temperature while you bake the donuts in batches.

In a bowl, whisk together both flours with the sugar, baking powder, salt, cinnamon and cardamom, until everything is evenly distributed.

Separately, whisk together the egg, sour cream and milk. Add to the dry ingredients, along with the melted butter and vanilla extract. Use a spatula to stir everything together into a thick batter.

Fill a 16-inch disposable piping bag with the batter, and snip off the tip. Pipe the batter into the greased donut pans, filling the molds half full. Don't overfill your donut pans, or the batter will spill over the molds, creating a little muffin top on the donuts.

Bake the donuts for about 12 minutes (for standard sized donuts) or around 8-10 minutes (for mini sized donuts), until the donuts spring back when gently touched. Cool in the pans for several minutes, then turn out onto a cooling rack.

In a bowl, combine the sugar and cinnamon. While the donuts are still warm, coat them in the cinnamon sugar.

Baker's Note: Sometimes baked donuts can have a slight "crust" on them right after baking, so that the sugar doesn't want to stick very well. You can opt to very lightly brush (do not dip or submerge) the donuts in melted butter, to help the sugar stick.But if you have the time to wait a bit, another easy solution, without adding extra butter, is to coat them in the sugar while warm, then place them in an airtight container. Place the lid on and let the donuts sit for at least 30 minutes to cool. The steam will be trapped inside the container, and the moisture will soften the crust on the donuts. Coat the donuts again in the cinnamon sugar, and it will stick much better.You can even bake the donuts the night before, store them in an airtight container at room temperature overnight, and coat them in the cinnamon sugar in the morning. They'll be just as soft and moist as they are when freshly baked.