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

In a large bowl, whisk together the flour, cocoa powder, baking powder, and salt.

In a separate bowl, cream the butter, granulated sugar, and brown sugar until light and fluffy.

Add the eggs one at a time, mixing well, then stir in the vanilla extract.

Gradually add the dry ingredients to the wet ingredients until just combined.

Fold in the chocolate chips.

Drop spoonfuls of dough onto the baking sheet, spacing them apart.

Bake for 10 minutes, then add marshmallows on top and bake for an additional 5 minutes.

Prepare icing by mixing powdered sugar, cocoa powder, milk, and vanilla.

Once cooled, drizzle the icing over the cookies and add sprinkles if desired.