01 -
Heat oven to 325°F. Line 9-inch square pan with parchment, leaving overhang. Spray with baking spray.
02 -
Heat butter, chopped chocolate, and 1 cup chips over medium-low until melted. Let cool slightly.
03 -
Whisk eggs, Nutella, sugar, and vanilla. Stir into warm chocolate mixture.
04 -
Mix in flour, baking powder, and salt. Fold in remaining chips and 1 cup nuts. Pour into pan and top with remaining nuts.
05 -
Bake 40 minutes, tent with foil, then bake 10-15 minutes more until just set. Cool completely before cutting.