Start by creaming ¾ cup of granulated sugar together with 4 tablespoon of softened butter.
Then add in 1 whole egg, 1 egg yolk and ½ teaspoon of vanilla and combine.
Next mix in ¼ cup + 2 tablespoon of Nutella and combine.
Mix in ½ cup of buttermilk then set aside.
In a small bowl sift together ¾ cup + 2 tablespoon of all purpose flour, ¼ cup + 2 tablespoon of Dutch process cocoa powder, ¾ teaspoon of baking powder, ⅛ teaspoon of baking soda, and ¼ teaspoon of salt.
Add the dry ingredients to the wet ingredients and combine.
Lastly mix in ¼ cup of hot coffee.
Line a cupcake pan with 14 cupcake liners and fill each cup ¾ of the way full. Bake the cupcakes at 350 degrees for 17-19 minutes, or until a toothpick/cake tester comes out clean from the centers and the tops "bounce" back when lightly tapped.
Let the cupcakes cool in the pan for 5 minutes then transfer to a cooling rack to cool completely.
For the Nutella Cookie Butter Filling
In a small bowl combine ¼ cup + 2 tablespoon of Nutella and ¼ cup + 2 tablespoon of cookie butter. Transfer the filling to a piping bag.
For the Cookie Butter Buttercream Frosting
Add 1 ¼ cups of softened, unsalted butter to a bowl and mix with an electric mixer until it is pale in color and fluffy.
Next add in ¾ cup + 2 tablespoon of cookie butter and combine until the mixture is fluffy.
Then add in ½ teaspoon of vanilla and ½ teaspoon of salt.
Slowly add in 2 ¼ cups of powdered sugar and mix until light and fluffy again.
Assembling the Cupcakes
Once the cupcakes are completely cooled remove a bit of the centers of each. Fill each with the Nutella cookie butter mixture.
Transfer the cookie butter buttercream to a piping bag fitted with a decorative tip. (My favorite to use is always my Wilton 1M tip).
Pipe a generous amount of cookie butter buttercream on top of each cupcake.
Drizzle each with Nutella and sprinkle chopped hazelnuts on top if you desire.
Serve! Store leftovers in an airtight container in the fridge for up to four days. (Let them come to room temperature before eating).
Notes
*Store leftovers in an airtight container in the fridge for up to four days. (Let them come to room temperature before eating).