To make the cookies:
In a microwave safe bowl, combine chocolate chips and butter.
Microwave in 30 second intervals, stirring well between each interval, until chocolate is all melted and smooth.
Let it sit and cool for 10-15 minutes.
In large bowl, combine flour, cocoa powder, baking powder, baking soda, salt, brown sugar, and granulated sugar, and stir to combine.
Pour chocolate into large bowl, and stir until combined. I used my stand mixer for this, and the following steps, but you could use a spatula.
Add eggs, one at a time, mixing until combined.
Finally, add the vanilla extract, mixing until combined.
Chill dough for 30-45 minutes.
Preheat oven to 325 degrees F.
Line baking sheet with parchment paper, and set aside.
Using small cookie scoop, shape dough into balls, and place onto prepared baking sheet.
Bake in preheated oven for 10-12 minutes.
Let cool on baking sheet for 5 minutes, then move to wire rack to cool completely.
To make the frosting:
Add heavy cream to small pot over medium heat.
Bring it to a simmer, then remove from heat and immediately add chocolate chips.
Let it sit for 2 minutes, then stir until completely combined.
Let cool for 10 minutes.
Place ~1 tablespoon of filling on one cookie, then top with another cookie.
Repeat with remaining cookies.