Step 1

Preheat oven to 340F (170C).

Step 2

In a small bowl whisk instant coffee and hot water. Set aside.

Step 3

In a large bowl, cream together butter and icing sugar. Add egg yolk and stir until combined. Add coffee and whisk until combined. Sift in flour, cornstarch, cocoa powder and salt. Stir until incorporated and dough is formed. Refrigerate for 20-30 minutes.

Step 4

Scoop out 1 teaspoon of the dough and roll then using your palms, shape them gently into an oval. Arrange then on a baking tray lined with a parchment paper. Then, using a toothpick or a back of a knife press it gently along the diameter of the oval.

Step 5

Freeze for 10 minutes or refrigerate for 30 minutes.

Step 6

Bake for 12 minutes. Allow to cool on a wire rack before serving.