|photo courtesy of slgckgc on Flickr.com|
Ugh! Me, too. Next time this happens to you, don't trash the cookies right away. If they're only burned on the bottom, you can possibly salvage them with your box grater:
Using the side with the smallest holes (the one used for zesting lemons or grating nutmeg), "grate" the black parts right off the cookie.
(This tip is from Sarah Moulton on an episode of the Rachael Ray show.)
Another tip to prevent cookies from burning on the bottom is to invest in a stoneware baking sheet. I use a Pampered Chef one from back in the day, but there are many new ones to choose from. If your cookies are burned on the bottom on that pan, they'll be burned all the way through. It really does heat evenly. It's a baker's best friend. :)