If you enjoy the combination of chocolate and coffee, you can definitely do this. Simply dissolve a teaspoon of instant coffee granules or espresso powder in the chocolate syrup mixture while it simmers on the stove. The coffee flavor will infuse into the syrup and enhance the overall taste of the cake. You can adjust the amount of coffee to your preference for a subtle or stronger coffee flavor. Proceed with the recipe as usual, and you'll have a delightful chocolate and coffee-infused biscuit cake.