Cupcake Directions:

1. Position rack in center of oven; preheat to 350°F.
2. Prepare cupcake tins with paper liners.
3. Combine cocoa powder and milk chocolate in medium bowl.
4. Pour boiling water over; whisk until mixture is smooth.
5. Whisk in buttermilk.
6. Whisk flour, baking soda, and salt in another medium bowl.
7. Using electric mixer, beat both sugars, oil, egg, and vanilla in large bowl until well blended.
8. Add flour and cocoa mixtures; beat until blended (batter will be thin). Divide batter between pans.
9. Bake cakes until tester inserted into center comes out with some crumbs attached, 15-20 minutes.
10. Cool in pans on racks for 5 minutes.
11. Let cool completely before filling with Nutella cream.

Filling Directions:

1. With a hand mixer, beat cold whipping cream until stiff peaks form.
2. Put Nutella in a small bowl, and fold/stir 1/4 cup of whipping cream into Nutella to lighten it.
3. Then, carefully fold the Nutella mixture into the remaining whipped cream mixture, so it remains light and fluffy.
4. Spoon the Nutella cream into a piping bag fitted with a filling tip (or a small star tip) and inject each cupcake with a small amount of filling.

Frosting Directions:

1. Bring a small amount of water to a rolling boil on the stove top in a large saucepan that allows the bowl of your stand mixer to sit atop the saucepan without touching the boiling water.
2. Whisk together egg whites and sugar in the bowl of your stand mixer. Place over rolling water (similar to a double boiler) and whisk constantly until the sugar is dissolved and no longer grainy (rub the mixture between your fingers to test).
3. Once the sugar has dissolved, immediately transfer bowl to stand mixer and whisk on medium high speed until the eggs form stiff peaks AND the bowl is cooled to room temperature.
4. Switch to the paddle attachment and add butter 2 pieces at a time until incorporated.
5. Continue to beat the mixture until it forms a smooth, silky frosting. If the mixture is runny or begins to curdle, do not fear – just keep beating until it comes together. This can take up to 10-15 minutes.
6. Once the mixture comes together, add the salt and vanilla extract and beat to combine.
7. Remove the bowl, and use a large spatula to carefully fold the Nutella into the frosting. Do NOT over mix – carefully fold the mixture just a few times to swirl the Nutella into the butter cream. You want to see streaks. I probably only stirred mine 4 or 5 times to reach the desired effect.
8. Carefully spoon the frosting into a large piping bag fitted with desired tip. Frost as desired, and garnish with a Ferrero Rocher candy.