For the Donuts
Preheat the oven to 350F/175C. Lightly grease a donut pan with oil.
In a medium sized bowl combine the wet ingredients: 1/2 cup full fat sour cream, 1 large egg, 1/2 teaspoon vanilla extract and 1/4 cup vegetable oil and 1/2 cup sugar. Whisk until fully incorporated.
Add in the 1 cup all purpose flour, 1/2 teaspoon baking soda, 1/4 teaspoon cinnamon powder, 1/4 teaspoon salt. Mix together until fully incorporated and a thick batter is formed. If you feel the batter is a bit too thick, then add 1-2 tablespoons of milk. However, the batter should be on the thick side, and not very thin.
Using a tablespoon, spread the batter evenly in each donut cavity. Alternatively you can pipe the batter into the donut cavities. I did not fill the donut cavities all the way up to the top, so I was able to get 8 donuts from this batter. However, if you want bigger donuts then you can fill the cavities till about full, but the donut holes will be slightly closed up if you do so.
Bake for 12-15 minutes, until the donuts are golden brown and springy to touch. Remove from oven and let cool in the pan for 10-15 minutes, and then remove the donuts from the pan.
For the Glaze:
Combine the 1 1/4 cups of powdered sugar, 1/4 cup milk and vanilla extract in a medium sized bowl. After the donuts have come to room temperature, dip each donut into the glaze and cover completely. Place on a baking rack so that excess glaze can be dripped.
The donuts can be stored upt o 3-4 days in the fridge in an airtight container.