Chocolate Cupcakes 

1. Preheat the oven to 350F(175C). Line (2) cupcake baking pans with 12-14 cupcake/muffin liners. Cupcakes may be baked in batches with (1) baking pan.
2. In a medium mixing bowl, add the flour, cocoa powder, baking powder, baking soda and salt. Whisk ingredients together to combine.
3. In the bowl of a stand mixer fitted with paddle attachment or with a hand mixer and a large mixing bowl, add the oil, yogurt and sugar. Mix ingredients together at medium high speed to combine, about 1 minute.
4. Next, beat the egg into wet batter at medium high speed until fully incorporated, about 30-60 seconds.
5. Reduce mixer speed to low. Starting and ending with the dry ingredients, mix half of the dry ingredients into wet batter followed by the espresso/ coffee and vanilla extract and ending with the remaining dry ingredients.
6. Stop the mixer and use a rubber spatula to scrape the sides and base of the bowl to catch any unmixed ingredients.
7. Resume mixing chocolate cupcake batter at medium speed for an additional 30-60 seconds. The resulting batter should be slightly thick and smooth.
8. Divide cupcake batter into prepared baking pan(s) and bake, rotating the pan(s) halfway through bake time for 16-18 minutes or until a toothpick inserted into the center of one of the cupcakes comes out clean.
9. Cool cupcakes in the pan(s) for 4-5 minutes before transferring to a cooling track to cool completely to room temperature.

Nutella Buttercream Frosting

1. In the bowl of a stand mixer fitted with paddle attachment or with a hand mixer and a large mixing bowl, cream the butter and salt at medium high speed until smooth and fluffy in appearance, about 2-3 minutes.
2. Next, mix in the nutella until it is thoroughly incorporated into the creamed butter.
3. Reduce the mixer speed to low and mix 2 1/2 cups of the confectioners’ sugar and cocoa powder into the nutella mixture. Gradually increase the mixer speed back to medium speed.
4. Once all the dry ingredients have been incorporated into the nutella mixture, mix in the vanilla extract until fully incorporated.
5. If buttercream appears to be on the soft side, mix in the remaining confectioners’ sugar 1/4 cup at a time until a thick but pipeable consistency is reached.
6. Increase mixer speed to medium high and mix Nutella buttercream frosting for an additional 30-60 seconds. The resulting frosting should be smooth and fluffy in appearance.

Assembly

1. Core the center out of cooled cupcakes. I used this cupcake corer.
2. Fill a pastry bag with the nutella spread and cut off 1/2 inch from the tip of the bag. Pipe enough Nutella to fill the center of cored cupcakes.
3. In a separate pastry bag fitted with your preferred pastry tip, pipe buttercream over the filled cupcakes in a swirl pattern/design. I used a Wilton 6B pastry tip.
4. Sprinkle piped buttercream with toasted hazelnuts before serving.