- 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.