Preheat the oven to 350°F (175°C) and line two baking sheets with parchment paper.

In a large bowl, whisk together the all-purpose flour, cocoa powder, baking soda, and salt. Set aside.

In another bowl, cream together the softened butter, granulated sugar, and brown sugar until fluffy. Then mix in the egg and vanilla extract.

Gradually fold the dry ingredients into the wet mixture, stirring gently until just combined.

To make the ganache, heat the heavy cream until it simmers, then pour over the dark chocolate chips and stir until smooth.

Scoop the cookie dough onto the prepared baking sheets, spacing them two inches apart. Bake for 10-12 minutes until edges are set.

Allow cookies to cool slightly on the baking sheet, then drizzle with ganache.