Coffee Syrup 1: While the espresso is still hot/warm, stir in the sugar. Let cool completely before using.
Coffee Syrup 2: Dissolve sugar and instant coffee in boiling water. Let cool completely before using.Coffee Syrup can be made a day in advance. Transfer to a container, cover and store in the refrigerator until ready to use.
Recipe by Foodie Baker at https://www.foodiebaker.com/opera-cake/