It uses aquafaba - which is just a fancy name for the water that you can pour off tinned chickpeas and beans. I was very skeptical about it at first but honestly, it's great. I find the water from lighter coloured beans the least "beanny" and if you can find unsalted or low salt beans, that's even better.
This dessert pairs well with champagne, but then again, so does everything. As it appears here the recipe is gluten-free, though of course feel free to use wheat based flour and pastry if you're not a coeliac.