Make the cookies: Preheat the oven to 350°F and line a baking sheet with parchment paper.
Melt the chocolate in the microwave in 15- or 30-second intervals, then set aside to cool slightly.
Add the cubed butter, sugar, and brown sugar to a mixing bowl or the bowl of the stand mixer fitted with the paddle attachment. Beat with a hand mixer or the stand mixer until creamed.
Add the milk and vanilla extract. Beat again until well combined. Beat in the cooled chocolate.
Add the flour, cocoa powder, baking powder, baking soda, and salt. Mix until just combined.
Split the dough into five equal pieces and roll into balls. Place on the baking sheet, leaving room in between each.
Bake for 11-13 minutes. Set aside to cool completely.
Make the glaze: Add all ingredients, minus vanilla extract, to a saucepan over medium heat. Whisk often until the mixture is melted and smooth.
Remove from heat and whisk in the vanilla. Allow to cool slightly.
Assemble the cookies: Top each cookie with some glaze. Top with some chocolate bits. Enjoy!