Usually only seen in the professional kitchen, feuilletine (foo-ye-teen, more-or-less, from the French "feuille," meaning "leaves") tastes like crispy, thin little shards of sugar cone. You can mix it in to mousses to add some crunch.
Mix into ganache and use for truffle centers. One of the keenest (?) uses is to mix it in to tempered chocolate to just barely coat it, spread it out thinly on silpat, let cool, then break up and use like crispy chocolate tuiles. Oh, my.
Here are some buying options for you (affiliate links):
Click the photo below to purchase 5.5 pounds--this is a big box. This stuff is light! Made by Cocoa Barry.
Click this photo to order a 4.4 pound box. Made by DGF.
You can also click below to order 11 oz. It is probably more cost effective to buy a larger container, but if you don't need much and don't plan on using it again, this gives you about 3 cups' worth.
If you're feeling Snazzy, The Brave Tart has a recipe up. Yes, you can make it yourself after all (although it might not be quite as ethereally thin and crisp as purchased, it will still be several cuts above using cereal)!
You can also make Crepes Dentelle and crush them up for feuilletine.