Preheat your oven to 350°F (175°C) and prepare your baking sheet by lining it with parchment paper or lightly greasing it.

In a mixing bowl, cream together softened unsalted butter and granulated sugar until light and fluffy, about 2-3 minutes.

Mix in vanilla extract and salt until fully incorporated, scraping down the sides of the bowl.

Gradually add in all-purpose flour, unsweetened cocoa powder, and dark chocolate chips, folding until a cohesive dough forms.

Fold in finely crushed mixed nuts, and chill the dough in the refrigerator for about 15-20 minutes if it’s too soft.

Shape the dough into small balls (about 1 inch) and place them on the prepared sheet, leaving space for spreading.

Bake for 12-15 minutes, allowing the edges to set while the centers might appear underbaked.

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

Optionally, dust the cooled cookies with powdered sugar for a decorative touch.