Preheat oven to 350 degrees. In a mixer fitted with the paddle attachment, mix butter on medium speed until creamy. Add salt. Mix in vanilla and coffee syrup. Add cornstarch and then with mixer set on low speed slowly add in flour and mix just until combine.
Scoop dough out 1 Tbsp at a time and roll into a ball and then press chocolate pieces in the middle of the ball, making sure to cover completely with dough. Place balls on greased baking sheets and bake in preheated oven for 16 – 18 minutes, until bottom edges are lightly golden.
Remove from oven and allow to cool several minutes then pour the powdered sugar into a bowl and roll cookies in powdered sugar.
Place cookies in airtight container, I usually add more powdered sugar prior to serving.