In a food processor or blender, puree strawberries until well-blended (there should be no discernible pieces).
Transfer the strawberry puree to a small saucepan over medium heat, add 2 Tbsp sugar and stir.
Cook, stirring frequently, until mixture begins to come to a slow boil.
Continue to stir while the mixture boils for about 10 minutes. The goal here is to cook the water out of the mixture so that you don't have a runny buttercream filling. As the strawberries lose their water, you may have to decrease your heat to prevent burning.
Cook about 10 minutes, or until mixture is about half of its original size (it will be like a paste)
Allow to cool completely before proceeding.
Once strawberry reduction has cooled, combine your butter and cream cheese in KitchenAid or in a large bowl.
Cream until well-combined.
Stir in vanilla.
Stir in 1 cup powdered sugar.
Add strawberry mixture and stir until well-combined.
Add cornstarch and continue to add powdered sugar, about 1/2 cup at a time, until well-combined.
If desired, add a drop of food coloring to enhance color.
Spread the buttercream mixture into a shallow dish (such as a 9x9 pan), cover with cling wrap and transfer to the refrigerator to chill for at least 2 hours or overnight.
Once buttercream filling has chilled, remove from refrigerator and lightly dust your hands with powdered sugar.
Roll into nearly 1 Tbsp-sized balls. The dough will be sticky and you will have to re-dust your hands with powdered sugar after every few candies. If the mixture becomes too sticky to manage, place in the freezer for 10 minutes.
Return to freezer for at least 10 minutes while you prepare your chocolate coating.
Melt chocolate according to instructions on packet. Remove your rolled buttercream filling from refrigerator and set it on the blade (width) of a butterknife. Pour chocolate over until covered, slide off of the knife onto a wax-paper-lined cookie sheet and immediately sprinkle with sugar (if using). Allow to harden.
Buttercream should be stored in an airtight container in the refrigerator, but I like the taste/texture best at room temperature so you may set out 15-20 minutes before serving to allow to come to room temperature.