Preheat oven to 350°F and line baking sheets with parchment paper or silicone baking mats.

In a microwave-safe bowl combine the chocolate and butter and microwave in 30-second bursts, stirring between bursts, until melted and smooth.

In the bowl of a stand mixer fitted with the whisk attachment, beat the sugar, eggs and vanilla on medium high for about 3 minutes, or until pale yellow and ribbony. Add in the melted chocolate and fold with a rubber spatula until combined. Add in the flour, baking, powder, and salt and stir until just combined and the flour has disappeared. The dough will be more like batter in consistency.

Let rest for about five minutes and then scoop dough onto prepared baking sheet about three inches apart. Bake for 8 minutes.

Let the cookies cool for 5 minutes before removing with a thin spatula to a wire rack to cool completely. Freeze the cookies until completely firm, at least 1 hour. The cookies can be stored in airtight containers in the freezer for up to 1 month.

To assemble, top one cookie with a scoop of ice cream. Place another cookie on top of the ice cream and gently press down to form a sandwich. Sprinkle the sandwich with a pinch of ground cinnamon, if desired. Immediately place the sandwich in the freezer. Repeat for the remaining cookies. Freeze for at least 2 hours before serving.

To store, wrap each sandwich in plastic and place in an airtight container. Store for up to 2 weeks in the freezer. Let sit at room temperature for 5 to 10 minutes to soften slightly before serving.