Preheat your oven to 350 degrees F and line 1-2 rimmed baking sheets with parchment paper. 

In a stand mixer on medium speed, cream together ½ cup of butter (1 stick) and brown sugar making sure to scrape down the sides of the bowl. Once mixed, add in egg, and vanilla extract. Mix until fully combined.

In a separate bowl, whisk together baking powder, gluten free flour and salt.

In 3 batches, add flour mixture to the wet ingredients and mix until a batter is formed while scraping down the sides. Batter will be very thick. 

In the microwave, melt ½ cup of chocolate chips in 30 second intervals and stir until all chocolate is melted. Add the melted chocolate to the dough mixture and mix on medium speed until the chocolate is fully incorporated. 

Using a tablespoon measure or small ice cream scoop, drop cookies onto the parchment lined baking sheet 2 inches apart. You may need to use 2 baking sheets to make sure they don’t spread into each other. 

Bake for 10-12 minutes. It’s important that they don’t over bake. When you take them out of the oven they may seem undercooked but let them cool and they will be the perfect texture. 

While cookies are completely cooling, make the chocolate icing by melting butter into a small saucepan. Add powdered sugar and milk and stir until a sauce texture forms. Sift in cocoa powder and stir until everything is evenly combined. 

Arrange cooled cookies right next to each other and crowd them together. Pour icing over the top of the cookies and make sure each cookie top is fully coated. Some icing will get in between the cookies and that’s ok.

Let icing fully set for about 1 hour before removing from the sheet and serving.