Here's what you need:
10 oz. chocolate
1/3 c. Karo Syrup
Variations : I usually use white chocolate, so I can color it what ever color I need. You can also use candy melts, (although I have never tried it.)
Tip: They say you should use the best quality chocolate you can buy, however, I have used chocolate chips with very good results. (Actually one time I tried to use a really good quality chocolate and for some reason it crumbled all over, and I had to throw it out.) So use whatever works for you.
Get your syrup ready, (I like to have a rubber spatula to help scrape it out.)Melt your chocolate. (Ok now here's where people will tell you to use a double broiler, blah, blah. But I have never had a problem in the microwave. The trick is to heat the chocolate in small increments, and stir it well until it's melted. Be careful or you can burn it.)
Mix your two ingredients together. After you stir for a few seconds it will thicken up to a more clay like substance. As you can see here it will be thick.
Put it in a zip lock baggie, get the air out and seal it up.
Leave it alone for at least 3 hours or so (overnight is fine). I like to leave it on my counter, but you can put it in the fridge.
Now you're ready to make something fun. It will be hard at first, (especially if you've put it in the fridge.) It will warm up in your hands. Form it in your hands just like clay.
Trick - you need to keep things cool or it will be too soft to work with, and the form will not hold. (I keep a little bowl of ice next to me, and cool off my hands every once in awhile. Also you can take a break and set it in the fridge to harden up for a bit.
The upside to using modeling chocolate instead of fondant:
When you make figures with fondant, (especially mmf) it is soft, and they tend to sink a bit. If you are using mmf you should make your pieces days in advance, and make them in separate pieces and put them together later.
With modeling chocolate, your figure pretty much stays how you make it, which is sometimes much nicer. It also gives you the freedom to make things bigger than you might be able to with fondant.
Once you get the hang of using modeling chocolate, you'll love it! You can make fun things and eat them too. Hopefully this helps someone, get out and make something fun.