In a large mixing bowl, cream together ½ cup of unsalted butter and 1 cup of powdered sugar until light and fluffy, about 3-4 minutes. Add one egg yolk and 1 teaspoon of vanilla extract, mixing thoroughly. Gradually incorporate 1 ½ cups of all-purpose flour, 2 tablespoons of cornstarch, and 2 teaspoons of instant coffee. Mix until a crumbly dough forms.

Press the crumbly dough together to form a smooth log and slice it into ½ inch cubes. Roll each cube between your palms to create an oval shape, mimicking coffee beans. Use a knife or toothpick to press a midline into each shape.

Place the cookie shapes on a parchment-lined baking sheet and chill them in the refrigerator for about one hour.

Preheat your oven to 350°F (175°C). Bake the chilled cookies for 12 minutes until they appear slightly golden around the edges.

After baking, allow the cookies to cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely.