A word of advice: pop the whole thing in your mouth, rather than trying to take a bite out of it, or it will drool gooey caramel all over you.
~1 1/2 lbs. bittersweet chocolate
1 cup sugar
1/3 cup water
1 Tbsp. light corn syrup
1/2 cup heavy cream
1/4 cup (1/2 stick) salted butter, cut into teaspoons
Temper about 1 lb. of the chocolate, and use it to coat the insides of about 6 dozen small paper candy cups. (Look in the yellow pages under "Candy making supplies" for a store that will sell these and, if you're reading this, lots of other things that you want.) I find a tiny little whisk to be a perfect tool for this (admittedly somewhat demanding and tedious) task.
Combine the sugar, water, and corn syrup in a large, high-sided, heatproof, microwavable bowl. (My 1-quart Pyrex measuring cup worked beautifully. You need something really heatproof, as caramelizing sugar is very, very hot.) Stir, cover loosely with plastic wrap, and microwave on high for 2 minutes. Remove from the microwave and stir until all the sugar is dissolved. You may need to return it to the microwave (re-covered) and heat it a bit more to get all the sugar into solution. When it's all dissolved, cover it again and microwave for 1-2 more minutes, until the steam has washed any crystals from the sides. Remove the cover and microwave on high until it's caramelized. This will probably take from 5-10 minutes, depending on your microwave. I'm afraid you'll have to watch it pretty closely during this process, as it can go from not done to horribly burnt surprisingly quickly. As soon as it starts to color, stop it and swirl to mix; do this a few times while it's browning, to prevent it from coloring unevenly. When the syrup reaches a dark amber color, remove it from the microwave. VERY SLOWLY, VERY CAREFULLY add the heavy cream, a little bit at a time, while stirring with a clean, long-handled wooden spoon. If you dump in too much cream all at once it will explode! The caramel is extremely hot at this point, and if you're not careful you will be horribly maimed. I accept no liability. Continue adding cream, very slowly and carefully, while stirring, until it no longer foams up. Then you may add the remaining cream in a slow, steady stream, while stirring constantly. Add the butter and stir until combined. Cool completely--this should probably be allowed to cool overnight.
With a regular spoon (i.e. a teaspoon, but not a measuring spoon), transfer about a half-teaspoonful of caramel into one of the cups. You want to avoid getting any caramel on the rim of the cup so that the chocolate can seal when you cap it. This is difficult at first, and nearly impossible to explain, (there's a bit of a trick involving twirling the spoon to make the ribbon of caramel break off) but pretty easy once you get the hang of it, so practice for a bit by just spooning caramel out of and into the bowl, then start filling cups once you can control where the caramel goes.
Temper the remaining bittersweet chocolate and, using a butter knife, add a cap of chocolate to close each cup. The texture of the chocolate will be best if you wait at least 24 hours.