Foam sauces have been around for a long time. Technically whipped cream and sabayon are foam sauces because of the air incorporated into then, but I realize that’s not what you are referring to.
From what I understand you start with a very flavorful essence or _base_ and then foam it. I have seen folks use the milk steamer from a cappuccino machine to do this. I believe that proteins by their nature can produce foams so using a milk as a substrate or possibly egg whites can do the trick.
I have never done this in production and even after doing a couple of Google searches could find very little information on this.