Step 1

In a large bowl, sift together the flour, baking powder, baking soda, cinnamon, and salt.

Step 2

In another bowl, mix the sugar, egg, egg yolk, and vanilla until pale and thick.

Step 3

Pour in the melted butter. Stir until combined. Add the sour cream in and whisk to just mixed.

Step 4

Pour the wet ingredients into the dry ingredients and gently fold in using a spatula.

Step 5

Turn the dough out onto plastic wrap and wrap it up tightly. Place in the fridge to chill for at least one hour.

Step 6

Once the dough has chilled, remove it from the fridge and turn out onto a lightly floured surface. Use a rolling pin to roll to about 1/2" thickness and use a donut cutter to cut out donuts (save the donut holes).

Step 7

Transfer cut out donut shapes to a parchment paper-lined cookie sheet and return to the fridge for at least 15 minutes.

Step 8

Fill a Dutch oven at least 2-3" deep with canola oil. Once the oil has reached 350-360°F, remove donuts from the fridge and transfer donuts or donut holes in the oil, just 3 a time. The donuts will float to the top. Then cook another 1-1 1/2 minutes and then use tongs or a slotted spoon to remove them from the oil and transfer to a paper towel-lined plate. The donuts should be a nice golden brown.

Step 9

To prepare the glaze, combine powdered sugar, milk, and vanilla. Whisk until smooth.

Step 10

Dip the warm donuts into the glaze and then transfer to a cooling rack to allow the glaze to set.