Preheat your oven 350 degrees.
In a medium bowl add the whole wheat flour, all purpose flour, baking powder, baking soda, salt, cinnamon and nutmeg. Whisk everything until fully combined, set aside.
In a separate large bowl, add the eggs, maple syrup and brown sugar and whisk until fully combined.
Add the skyr, vanilla and mashed banana and give everything a good whisk until fully combined.
Pour the butter and canola oil and whisk until fully combined.
Gently fold in the dry ingredients into the wet mixture and fold until no more dry pockets remain.
Pour the batter into a large plastic icing bag or large Ziploc. Once ready to pipe, snip the edge of your plastic bag. Fill each cavity of your donut pan 2/3 of the way, the donut will rise as it bakes up.
Bake the donuts for 8 minutes or until a toothpick come out clean without any wet batter. Let the donuts cool for about 10 minutes. Remove them from the pan and fill the donut pan with the rest of the batter and bake.
Once all the donuts have baked and cooled, make the cinnamon sugar coating. Add the sugar, cinnamon and salt.
Dunk the top of each donut in the melted butter very gently. Dip each donut into the cinnamon sugar mixture until the majority of the donut surface is covered in sugar. If you like a sweeter donut, feel free to sprinkle more sugar on top.
Enjoy! Any leftover donuts will last for about 2 days once coated in sugar.