What you're about to read has been highly guarded by the super mega corporate chocolate producers of the world. The short of it is that despite the ultra-complex images of chocolate factories you may have seen (Willy Wonka's included), high quality dark chocolate is very easy to make all by yourself in your own kitchen in a matter of hours. In the interest of not listing multi-hundred dollar pieces of equipment, the chocolate you will end up with will have a rustic texture, and will be excellent for eating and cooking.
A normal household oven
A baking sheet that will fit in the oven
A kitchen scale
A hair drier
A Champion brand juicer (or similar auger style--I have a Solo Star II)
A rubber spatula
Aluminum foil or parchment paper
A coffee grinder (cheap whirly blade type, not the fancy burr type)
A friend (choose wisely since you will have to share your chocolate with this person :)
16 oz unroasted whole cocoa beans (if you can only find roasted, just skip the roasting step). You can find these at health food stores like Whole Foods.
***If you only have nibs available, get roasted ones and skip to Step 3.***
Granulated white sugar (DO NOT use powdered sugar --it contains corn starch, and you don't want that in your chocolate)
Step 1: Roasting
Roasting the cocoa beans is essential to develop the "chocolate" flavor. Its also pretty easy to do (there is a lot of science to roasting cocoa, but we won't get into that here)
1. Adjust an oven rack to the middle position and pre-heat your oven to 300F.
2. Spread your unroasted beans out on your baking sheet so they are in a single layer.
3. Once the oven is preheated, place the pan in and start your timer. Roast the beans for 30 minutes. For your first time trying this, pay close attention to the smell. When your beans first start heating, you might notice an acidic smell coming off--this is normal. What we want to do is cook that off and wait until they start smelling like brownies. Because there are endless variations on how to roast and beans vary in how much they should be roasted, I've suggested a very "average" roast. You can experiment with future batches.
4. At 30 mins, pull the beans out and place the pan in front of a fan to cool. If you don't have a fan, don't worry, just let them cool until they are cool enough to handle.