Line two baking sheets with parchment paper; set aside. In the bowl of an electric mixer fitted with the paddle attachment, cream butter and sugar on medium-high speed until light and fluffy, about 3 minutes.
In a small bowl, stir espresso powder into 2 teaspoons hot water until coffee has dissolved. Add
coffee mixture and ground espresso beans to butter mixture; beat to combine.
In a medium bowl, whisk together flour and salt. Add to butter mixture, and beat on medium low speed until well combined, about 4 minutes. Cover with plastic wrap, and refrigerate until well chilled, at least 2 hours or overnight.
Preheat oven to 325 degrees. Shape heaping tablespoons of dough into ovals. Arrange ovals about 1 1/2 inches apart on prepared baking sheets. Using a wooden skewer dipped in flour, make an indentation in dough lengthwise to achieve the look of a coffee bean. Freeze or refrigerate until firm, about 20 minutes.
Bake, rotating sheets halfway through, until cookies are just beginning to brown, 16 to 18 minutes. Transfer cookies to a wire rack to cool completely. Store up to 1 week in airtight containers at room temperature.
To give these cookies a stronger coffee flavor, add 2 teaspoons of coffee extract after creaming the butter and sugar.