Instead of instant espresso in Coffee and Walnut Cake

Hello, 

You can use granulated instant coffee dissolved in a minimal amount of freshly boiled water. 

You could heat a cup with boiling water, discard the water then put a heaped tablespoon of coffee granules in the cup, quickly followed by a tablespoon of boiling water and whisk with a mini whisk (or fork) until dissolved (or you could use a microwave). 

Let it cool a bit before you add it.

Best wishes

Lindsey