In a large bowl, cream together butter and sugar with a mixer. Add egg and vanilla. Mix making sure to scrape down the sides and bottom of the bowl with a spatula combine all the ingredients evenly.

Add the cocoa powder, espresso powder, and salt. Mix to combine. Let sit 5 minutes to allow the espresso powder to release it's flavor.

Gradually add the flour to the butter mixture until completely combined. Turn out the dough onto a lightly floured surface. Knead the dough gently one to 2 times.

Form a log of dough roughly 2-3 inches in diameter. Roll in sprinkles now if desired. Wrap dough log in plastic wrap and refrigerate at least 4 hours to chill completely. Dough can be stored in the fridge for up to a week.

When ready to bake the cookies, preheat oven to 350F. Remove dough from the refrigerator and plastic wrap. Slice into 1/4 inch slices.

Place on a parchment-lined baking sheet and bake 10-12 minutes or until the edges just start to turn light golden brown.

Let cool on the baking sheet 2-3 extra minutes. Remove and enjoy!