Preheat oven to 175°Celsius.
Line baking trays with parchment paper.
Prepare the coffee solution by mixing instant coffee granules with hot water. Stir to dissolve completely. Set aside to cool.
In a medium-sized bowl, cream the butter, brown sugar and granulated sugar until creamy.
Add the egg yolk and continue beating until all traces of the egg are no longer visible.
Add the coffee mixture and beat again.
Add in the flour and mix until the flour is well incorporated.
Add two-thirds of the coffee chips and dark chocolate chips. Mix well.
Scoop the cookie dough into 1 tablespoons sizes. Shape them into round balls with hand.
Place the cookie balls well apart from one another on the baking tray. Press the remaining coffee and chocolate chips onto the cookie balls.
Bake for 6 minutes for soft and chewy cookies. Continue baking until 10 minutes for a light and crunchy cookies.
Remove cookies from the oven. Let them rest in the baking tray for a few minutes before transferring them onto a wire rack to cool completely. Store in an airtight container.