This as one reviewer noted is the holy grail of icing recipes… it should be it's been around for a long time. Some reviews wrote that the icing didn't totally dry and some said that it wasn't shinny enough. The secret is in the mixing of the syrup and milk. Use whole milk and light syrup in a 50/50 ratio. It takes a bit of practice. If you add too much milk you will lose some of the shine and too much syrup will keep it from hardening. Once you get it right you'll never use another icing…
FYI: Using lemon extract in place of the almond as suggested gives the icing a light taste that balances quite well against a typical sugar cookie.