Preheat oven to 350° F. Grease a 9 X 13″ baking pan.
In a large microwavable bowl, place semisweet chocolate chips and butter. Cook on high for 2 minutes. Stir mixture with wooden spoon until all of the chips and butter are melted.
In the bowl of a standing mixer, combine the sugar, flour, salt and baking powder. Stir to mix thoroughly.
Add the eggs and vanilla to the chocolate mixture, blending well with a wooden spoon.
Pour this mixture into the bowl with the dry ingredients. Mix on medium speed for 30 seconds, just until ingredients are blended. Stir in the milk chocolate chips and 1/2 cup hazelnuts. Spread into prepared pan. Sprinkle with remaining hazelnuts.
Bake until the brownie starts to come away from the sides of the pan, about 35 minutes. Cool before cutting to serve.
Serve with your favorite ice cream!