In large bowl, using KitchenAid or Hand Mixer, cream together butter and cream cheese on medium-high speed.
Beat in brown sugar on high speed until well-combined (about 1 minute), pausing to scrape down the sides of the bowl with a rubber spatula to make sure all ingredients are well-incorporated.
Stir in vanilla extract.
Add flour and gradually stir in flour and powdered sugar (only about 1/2 cup powdered sugar at a time), pausing to scrape down sides of bowl as needed until all sugar has been stirred in completely.
Add heavy cream and beat on medium speed until well-combined.
Stir in chocolate chips.
Cover bowl with clear wrap and refrigerate. The dough may be manageable as soon as 2-3 hours after being transferred to the refrigerator, but if not you may have to wait as long as 5-6 hours (it will be fine to sit overnight, as well).
Once dough is manageable (if it is too stiff, allow it to sit at room temperature for 10 minutes before you begin rolling) roll dough into 1 1/2 tsp sized balls between the palms of your hands. Transfer to wax-paper lined plate and set in the freezer while you prepare the chocolate (they should sit in the freezer for at least 5-10 minutes, but should not be frozen).
Prepare chocolate by melting in large bowl for 30 seconds, stirring, and then repeating at 15 second intervals until chocolate is completely melted.
Dip buttercreams in chocolate***, transfer to wax-paper lined surface and allow the shells to harden before serving.