Line a large baking sheet with parchment paper. In a medium bowl, whisk together the flour and cocoa until well combined. In another bowl, beat the butter, sugar, vanilla and ground coffee beans until lightened and well combined.
Mix in the flour and cocoa until a soft dough forms. With your hands, roll the dough into 3/4-inch (2-cm) round balls. Flatten and shape each dough ball into a 1/2-inch (1-cm) thick oblong and place on the baking sheet, leaving a 2-inch (5-cm) space between each cookie.
Using the dull side of a dinner knife, score a deep line lengthwise down the centre of each cookie. Chill the cookies in the fridge for 20 minutes. Preheat the oven to 300 degrees F (150 degrees C).
Bake for 15 to 18 minutes, or until the cookies are slightly firm to the touch and just cooked through.