Preheat the oven to 350°F (180°C). Spray a mini donut pan with nonstick spray and set aside.
In a bowl, whisk together the melted butter, oil, brown sugar, granulated sugar, and corn syrup.
1/4 cup salted butter, melted, 3 tbsp canola oil, 1/4 cup granulated sugar, 1/2 cup brown sugar, 1 tbsp corn syrup
Whisk in the egg and then the sour cream until smooth.
1 egg, 1/4 cup sour cream
Add the milk and vanilla, mixing until combined.
1/3 cup milk, 2 tsp vanilla
Add the remaining dry ingredients to the bowl and whisk and then stir until a thick batter is reached.
1 3/4 cups flour, 2 tbsp corn starch, 1 1/4 tsp baking powder, 1/2 tsp salt, 1/8 tsp nutmeg
Transfer the batter to a piping bag or a gallon zip top bag with the corner snipped.
Pipe the batter into the prepared mini donut pan, filling each cavity approximately ½ full.
Bake at 350°F (180°C) for 4-5 minutes or until the donuts have risen and feel soft but firm when tapped.
Immediately flip the pan over to remove the donuts from the pan. Repeat with remaining batter, if needed.
While the donuts are still warm, coat each donut with powdered sugar. I recommend dumping the powdered sugar into a ziptop bag with a few donuts at a time and shaking until they are completely coated.
2 cups powdered sugar
Allow the donuts to cool at room temperature.
Store in an airtight container for up to 2 days. Enjoy!