Yes, instant coffee can be used as a substitute for espresso in this recipe. To incorporate instant coffee, dissolve the desired amount of instant coffee granules in hot water, following the instructions on the coffee packaging.  Then, use this prepared instant coffee to replace the espresso in the recipe. Remember that the strength and flavor profile may differ slightly from brewed espresso, but it will still provide a coffee element to the Biscoff Tiramisu. Adjust the amount of instant coffee according to your taste preferences and the desired level of coffee flavor in the dessert.