Preheat the oven to 325°F. Lightly spray an 8x8 baking dish with cooking spray and line it with two pieces parchment paper so it can easily be removed after baking to cut.
In a medium bowl, whisk together the sugar, flour, cocoa powder, powdered sugar, and salt.
1½ cups granulated sugar, 1 cup all-purpose flour, ⅔ cup dutch-processed cocoa powder, ½ cup powdered sugar, ¾ teaspoons kosher salt
Using a stand mixer or hand mixer, whisk together the eggs, oil, and water for 2 minutes on medium high speed.
2 large eggs, ½ cup canola oil, 2 tablespoons water
Add the dry ingredients and chopped chocolate to the wet ingredients and fold in by hand until just combined.
½ cup semi-sweet chocolate
Pour half of the batter into the prepared pan and use a spatula to smooth the top.
Melt the nutella in the microwave for ~20 seconds, then spread it evenly over the first brownie layer.
½ cup Nutella
Unwrap the ferrero rocher and press them into the batter in a 4x4 grid.
16 Ferrero Rocher candies
Add the remaining brownie batter, spreading it to meet the edges.
Note: it will be a very thin layer and will take a bit of patience to spread it the whole way. It’s best to add it in between the ferrero rochers rather than trying to get it over top of each.
Bake for 45 to 60 minutes, until the edges are set, and the center still looks soft. Cool completely before slicing.