Preheat your oven to 180C/160C Fan, and prep your cupcake cases. I used Iced Jems baking cups so just put them on a flat tray.
Beat together your butter and sugar until light and fluffy, and then add in the flour, cocoa powder, and eggs.
Beat again until smooth, then split evenly between the cases. I use an ice cream/cookie scoop to get them all equal.
Pop a Ferrero Rocher on top of each cupcake, and push it in ever so slightly.
Bake in the oven for 17-20 minutes, or until baked. Cool completely.
Beat the unsalted butter (best at room temp), for a couple of minute until smooth.
Add in the Nutella and beat again briefly.
Add in half of the icing sugar and beat, and then the other half and beat.
If its too thick, add in 1tbsp of boiling water at a time till it becomes pipeable.
I used a large round tip, and piped my Nutella Buttercream on, and then sprinkled on some hazelnuts, and popped another Ferrero Rocher on!
Notes
The Ferrero Rocher that are hidden inside the cupcakes are optional - or the ones on top are. You can easily just do one of them, as buying 24 Ferrero Rocher can be expensive if they're not on offer!
Alternatively, you can just make these regular cupcakes, like my Nutella cupcakes.