Preheat the oven to 350ºF. Line a sheet tray with parchment paper or a Silpat.
In a large bowl, whisk together the egg whites, vanilla, cinnamon, flour and sugar. The batter will be very loose.
Using a small spoon, scoop about 1 tablespoon of batter onto the lined cookie sheet. Use the back of the spoon to smooth the batter into a very thin circular layer. Repeat this process with additional batter to form two or three circles of batter on the cookie sheet. (See Notes below.)
Bake the cookies for 5 to 7 minutes, or just until the edges of the cookies begin to brown.
Remove the cookies from the oven, place the handwritten fortunes in the centers of the cookies, and then use a flat spatula to very carefully release the cookie from the sheet tray.
Fold it in half, then pinch the edges inward (as shown above) to create the fortune cookie shape. Continue this process with the remaining cookies, which will harden within 30 seconds of being formed.
As an optional garnish, melt the chocolate chips in the microwave in 20-second intervals then dunk the hardened and cooled cookies into the chocolate. Immediately decorate the chocolate-dipped cookies with sprinkles and let harden.
It may seem tedious to only portion out one or two cookies per batch, but I found that trying to bake three or more cookies and shape them all before the last one completely hardened was difficult to do. Baking the cookies in batches of one or two guarantees you'll have enough time to fold them into the perfect fortune cookies.