How to make "solid" foam

Nick_192744

I was watching this video where the chef makes a lime/lemongrass foam cube. Any thoughts on how this was made: https://youtu.be/5Qo6741sjG8?t=1m33s ?

John_H_637272

You can infuse lime and lemon grass into light simple syrup. Bloom some gelatin leaves, and put it in a kitchen aid with a whisk and whip until a stiff peak forms. Then set it in a tray, probably dusted with cornflower or icing sugar to prevent sticking.. You are essentially making a marshmallow. I am by no means a pastry chef, but that's what I would try