Preheat oven to 350 degrees. Line a cupcake pan with 12 liners and set aside.
In a small bowl sift together all purpose flour, Dutch process cocoa powder, baking powder, baking soda, and salt. Set aside.
Add granulated sugar and softened butter to a large bowl. Cream together with an electric mixer for 1-2 minutes until fluffy.
Then add in the egg, egg yolk and vanilla and mix until light and fluffy, about 1-2 minutes.
Next mix in the milk and sour cream.
Add the dry ingredients to the wet ingredients and combine.
Lastly mix in the dissolved instant coffee (optional.)
Fill each cupcake well ¾ of the way full with batter. Bake the cupcakes for 17-19 minutes, or until a toothpick/cake tester comes out clean from the centers.
Let the cupcakes cool in the pan for 5 minutes then transfer to a cooling rack to cool completely.