Sweet green grapes are another favorite snack of mine and they're a great party food because most people really like them. For this more upscale dish I turn them into a sweet, fizzy soup. The xanthan gum helps hold the particles in suspension and the carbonation effect adds a pleasant tingle and tang to it.
This is a pretty sweet soup so I usually try to keep the portions small. You can make it up to two days ahead of time if you refrigerate it in the whipping siphon, but you only have 10 to 20 minutes to serve it once you have opened the siphon. If you want a more refined presentation you can strain the soup after pureeing it, though I'd wait to add the xanthan gum until after it's strained.
If you like this recipe you can get more than 80 other recipes from my book Modernist Cooking Made Easy: Getting Started. The book covers many of the popular modernist techniques such as gelling, spherification, and foams. It also explores modernist ingredients like agar, sodium alginate, tapioca maltodextrin, and xanthan gum. It is all presented in an easy to understand format and I think it's the best way to learn about modernist cooking.
Also, if you are just getting started experimenting with molecular gastronomy and modernist cuisine then I highly recommend one of these molecular gastronomy kits. They have everything you need to do many different dishes.
Place all the ingredients in a blender or food processor. Processes until everything is broken down and it is nice and smooth. Pour into a whipping siphon and fully charge it with CO2. Place in the refrigerator until ready to serve, at least one or two hours.
Place a cloth over the nozzle, vent the whipping siphon, then open it. Pour some of the soup in a dish and top with a several grape halves and almond slivers.