If you make them, tell us how they are. I haven’t made them yet, but they looked like an elegant little easy-to-make thing.
I'm sure you can make them with confidence. Only I would use vanilla wafers. And it is sometimes difficult to get enough coffee flavor to come through. I haven't found using instant always satisfactory, and if you use brewed coffee, it's never strong enough.
I need to get some fresh instant espresso which I keep in the freezer.