Preheat the oven to 350 degrees (F). Line a 12-cup cupcake/muffin tin with cupcake liners and lightly spray the liners with non-stick spray (optional but it does help them peel right off).

Melt the oil, butter,and chocolate together in the microwave, heating in 30 second increments, and stirring between increments each time. You can also melt the oil, butter, and chocolate over very low heat on the stovetop, but I find the microwave to be much easier. Whisk mixture until completely smooth and set aside to cool.

In a medium sized bowl combine the flour, baking soda, baking powder, cocoa powder, and salt; stir together until thoroughly combined; set aside.

In a large bowl, whisk together the eggs, yolk, sugar and vanilla together; beat until smooth. Add the cooled oil/butter/chocolate mixture and whisk until smooth. Add half of the flour mixture, then half of the sour cream. Repeat the process until everything is added, and be sure to mix until JUST combined - then quickly stir in the hot coffee/water. It's important not to over mix, here! Just stir until evenly combined.

Divide the batter among the 12 liners in your prepared pan. Bake for 16-18 minutes, or until a toothpick inserted in the center comes out clean. Cool *completely before frosting.

Sift together the confectioners sugar and cocoa powder, whisking well to ensure it's bump and lump free!

Using a handheld mixer OR a stand mixer fitted with the paddle attachment, beat the butter on medium-high speed until creamy; about 2 minutes. Reduce speed to low and slowly add the sifted sugar/cocoa powder, alternating with the Nutella and milk, then add the vanilla and salt. Once all of the ingredients have been added, beat on high speed until light and creamy and combined; beat for at least 1 minute on high.

Frost cooled cupcakes and top with any decorations if desired.

Cupcakes stay fresh at room temperature in an airtight container for up to 4 days.

Place chocolate chips in a wide and shallow heat proof bowl. Heat the cream in a small sauce pan over medium-heat. Bring to a boil, watching very carefully as it will happen fast. When the cream has come to a boil, remove from heat and pour over the chocolate chips. Allow the cream and chocolate to sit for minute, then whisk completely smooth. Let the ganache cool for a few minutes before you drizzle it over the cupcakes. Press a Ferrero Rocher candy on top of each cupcake and allow the ganache to set a few minutes before serving.