Preheat oven to 300F. Line baking sheets with parchment or silpats (see note). Set aside.
In the bowl of a stand mixer, combine butter, sugar, and salt. Beat just to combine (you don't want to work too much air into the mixture).
Add flour and ground espresso beans. Mix until the dough starts to come together. Turn the dough out onto the counter and knead gently if necessary.
Roll the dough out to about ¼" thick on a lightly floured surface. Cut out cookies and place on prepared baking sheets. Scraps can be gathered and re-rolled to cut more cookies.
Bake cookies until they appear dry and are slightly browned, 30-35 minutes. Allow the cookies to cool on the baking sheet five minutes, then remove to a wire rack to cool completely.
Line a baking sheet with waxed paper. Dip the cooled cookies in chocolate, then place on the prepared sheet to set. Once set, use a small paintbrush to apply luster dust, if desired.Enjoy!
Notes
Note on silpats: I use silpats to line my pans because the cookies don't brown as quickly (I hate it when cookies overbrown!) and because I can wash and use them again and again. If you don't have any and you're in the market for some, you can find them online [here]. Note on espresso beans: I found finely ground espresso beans at my local grocery store. If you can't find ground espresso beans at your local store, you can find them [here]. Alternatively, you could substitute espresso powder, the espresso powder will just incorporate more fully into the dough (no flecks of espresso bean).