In a mixing bowl, combine 2 tablespoons of instant coffee, 1 cup of softened unsalted butter, and ¾ cup of powdered sugar. Use a hand mixer on medium speed to cream until light and fluffy (about 3 minutes). Gradually add 1¾ cups of cake flour, 2 tablespoons of cornstarch, and 1 egg yolk. Mix until the dough is smooth (1-2 minutes).

Turn the dough out onto a floured surface. Roll into a log shape and cut into ½ inch cubes (about 8 grams each). Shape each cube into an oval resembling a coffee bean and create a slight indent down the center.

Place cookies on a parchment-lined baking sheet with space between. Cover with plastic wrap and refrigerate for about 1 hour to maintain shape and texture.

Preheat the oven to 350°F (175°C). After chilling, arrange cookies on a lined baking sheet and bake for 12 minutes or until edges are lightly browned.

Let cookies cool on the baking sheet for about 5 minutes, then transfer to a wire rack to cool completely.