Bring wine, sage leaves and shallots to boil and simmer for five minutes. Blitz mixture, pass through a fine sieve and measure how much liquid you have left.
Add soy lecithin powder (2g to every 250ml) and blend well in a high container, strain again and keep until needed.
To serve, move the emersion blender to the upper part of the liquid surface to incorporate as much air into the foam as possible. Once you have enough foam, leave to rest for 1 minute so the excess liquid is eliminated.
Spoon on to dish as needed.