Preheat the oven to 350°F. Line a baking sheet with a silicone mat or parchment paper and set it aside.

In a mixing bowl, use a hand mixer to blend the butter and sugar until well combined.

Mix in the eggs and vanilla extract until fully incorporated.

Sift together the flour, cocoa powder, baking soda, and salt. Gradually add this mixture to the wet ingredients, stirring until well mixed.

Stir in 1 cup of mini milk chocolate chips and 1 cup of chopped toasted hazelnuts.

Scoop out heaping tablespoon-sized portions of dough, roll them into balls, and place them on the prepared baking sheet.

Gently flatten each dough ball with your palm to about half an inch thick. Top with a few additional milk chocolate chips and chopped hazelnuts.

Continue shaping and topping the cookies, leaving two inches of space between them on the sheet. Bake for 12 minutes.

Remove the cookies from the oven and let them cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.