1. Preheat oven to 350°F (175°C) and line a baking sheet with parchment paper.

2. In a large bowl, cream the softened butter and brown sugar until light and fluffy.

3. Beat in the egg and vanilla extract until fully combined.

4. In a separate bowl, whisk together the flour, cocoa powder, baking soda, and salt.

5. Gradually add the dry ingredients to the wet ingredients and mix until a soft dough forms.

6. Roll tablespoon-sized portions of dough into balls and place on the baking sheet, spacing 2 inches apart.

7. Slightly flatten each dough ball with your fingers or the back of a spoon.

8. Bake for 8–10 minutes until the edges are set but centers remain slightly soft.

9. Let the cookies cool completely on a wire rack.

10. Melt the dark chocolate and drizzle generously over cooled cookies.

11. Sprinkle chopped roasted hazelnuts on top while the chocolate is still wet, gently pressing to help them stick.

12. Let cookies set at room temperature or refrigerate briefly until chocolate is firm.