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

In a large mixing bowl, whisk together flour, cocoa powder, baking soda, and salt until well combined.

In another bowl, cream together butter, granulated sugar, and brown sugar for about 3-4 minutes until fluffy.

Add in the egg and vanilla extract into the creamed mixture and beat until smooth.

Gradually add the dry mixture to the wet ingredients, stirring until just combined, then fold in the mini chocolate chips.

Scoop tablespoon-sized portions of dough, flatten each into a disk, and place a marshmallow in the center, wrapping the dough around it.

Place the dough balls about 2 inches apart on the prepared baking sheets.

Bake for 10-12 minutes until the edges are set and the centers remain soft.

Allow the cookies to rest for about 5 minutes on the baking sheets before transferring them to wire racks.

Melt chocolate chips, heavy cream, and butter in a microwave-safe bowl, then drizzle over the cooled cookies.