Prepare the Butter: In a large skillet or saucepan, melt the butter over medium heat until it turns golden brown, about 5-7 minutes. Watch carefully to prevent overheating. Once the butter has a brown hue and a nutty aroma, remove it from the heat and let it cool to room temperature.

Make the Dough: In a large bowl, mix the cooled brown butter with brown sugar and granulated sugar. Beat until smooth. Add the eggs and vanilla extract, continuing to beat until the mixture is uniform.

Combine Dry Ingredients: In another bowl, mix the flour, baking soda, baking powder, and salt. Gradually add the dry ingredients to the wet mixture, stirring until a uniform dough forms. Then fold in the roasted and chopped hazelnuts and chocolate chips, gently mixing to evenly distribute.

Chill the Dough: Cover the bowl with plastic wrap and chill in the refrigerator for at least 1 hour to firm up the dough.

Preheat the Oven: Preheat the oven to 350°F (180°C). Line a baking sheet with parchment paper or a silicone mat.

Form the Cookies: Form dough balls about the size of a walnut and place them on the baking sheet, leaving enough space between them to expand during baking. About 5 cookies per baking sheet.

Bake: Bake the cookies in the preheated oven for about 10-12 minutes, or until they start to turn golden at the edges. They will be soft in the center when removed from the oven but will firm up as they cool.

Cool: Cool the cookies on the baking sheet for 5 minutes, then transfer them to a wire rack to cool completely.