Preheat the oven to 350℉/180℃. Grease an 8×8 inch square pan. For easy removal of the brownies, place parchment paper on the bottom and 2 sides of the pan. Grease again and then set side.
In a large bowl, add melted butter and white sugar until well combined. It will look glossy, but have grains which is okay.
1/2 cup butter, 1 cup white sugar
Add eggs and vanilla and continue whisking.
2 eggs, 1 tbsp vanilla
Toss in flour, salt, and cocoa powder. Using a spatula, mix until a brownie batter forms. Don't overmix!
3/4 cups all-purpose flour, 3/4 cups unsweetened cocoa powder, 1/2 tsp salt
Add in the chopped hazelnuts and Ferrero Rochers and mix in.
12 Ferrero Rochers, 1/4 cup hazelnuts
Transfer into the prepared pan and spread evenly. Top with extra halves of Ferreros.
Bake the brownies for 30-35 minutes. A toothpick inserted should come out fudgy. If it is wet, it isn't ready yet. Continue to bake at 5 minute intervals until fudgy in the middle, and the edges are set.
The brownies continue to bake as they cool in the pan. Allow them to sit until cooled. Slice, and enjoy!
Store the brownies on your counter for 3 days or in the fridge in an airtight container for 7.