01 -
Heat oven to 325°F. Line a square 9-inch baking pan with parchment paper, making sure there’s about a 2-inch edge hanging over all sides. Lightly coat it with nonstick spray.
02 -
In a medium pot over low heat, stir together the butter, 4 ounces chopped chocolate, and 1 cup chocolate chips. Keep mixing until smooth, then set aside to cool down.
03 -
In a big mixing bowl, beat together the eggs, Nutella, sugar, and vanilla until well combined. Slowly mix this into your warm chocolate mixture.
04 -
Combine flour, baking powder, and salt by sifting them together. Mix this dry blend into your chocolate batter. Then, fold in the rest of the chocolate chips and 1 cup toasted hazelnuts.
05 -
Pour the batter into the prepped pan and scatter the other half of the hazelnuts on top. Bake for 40 minutes, then loosely cover with foil and bake another 10 to 15 minutes until mostly set. Let it cool fully before slicing.