Preheat the oven to 350°F and line a baking sheet with parchment. You’ll thank yourself later.
Whisk together flour, cocoa powder, espresso powder, baking soda, and salt. No lumps allowed.
Beat melted butter, brown sugar, and granulated sugar until smooth. It should look dangerously good.
Mix in the egg and vanilla extract. Blend until fully combined.
Gradually add the dry mixture to the wet ingredients. Stir just until combined—overmixing kills cookies.
Fold in chocolate chunks and hazelnuts. Try not to eat all the dough.
Scoop tablespoon-sized portions onto the baking sheet, spacing them 2 inches apart. No cookie pile-ups.
Bake for 12 minutes, or until edges are set but centers remain slightly soft.
Cool on the baking sheet for 5 minutes, then transfer to a rack. Or just eat them now.
Pair with coffee, milk, or straight from the tray. No wrong choices.