You can't really make a fine semi-sweet homemade chocolate bar from cocoa powder, but you can make a reasonable approximation that you can substitute for baking chocolate in recipes and to eat cold out of the refrigerator. Although chocolate connoisseurs may scoff at this approach, even homemade chocolate is still chocolate – and you really can't go wrong with chocolate.
Gently melt fat, such as butter or cocoa butter, which are solid at room temperature. Add cocoa powder and sweetener and mix thoroughly. Put the mixture in the freezer or refrigerator to set. Use no more than 50 percent sugar to make it semi-sweet.
What Is Cocoa Powder?
Cacao is the raw ingredient that is processed into cocoa powder and cocoa butter. The cacao plant grows in tropical regions and produces pods filled with cacao beans. These are removed and fermented before being roasted, winnowed (separating the shells from the edible portion), cracked and ground into a viscous chocolate liquor. This liquor is made up of about 50 percent fat, though the exact fat content depends on the genetics of the beans.
Chocolate liquor can then be fully ground in a machine called a melanger, which does its work for 24 to 72 hours until the chocolate is fully smooth. Or, it can be separated into cocoa powder, which contains no fat, and cocoa butter, which is entirely made up of fat. This can be done through a natural process of pressing, or by a chemical process that involves washing the cacao in an alkaline solution to make a product known as Dutch processed cocoa.
How to Make Homemade Chocolate
Any homemade chocolate recipe using cocoa powder involves some method of combining the two elements of unprocessed cacao that have been separated to create the cocoa powder. If you make chocolate from cocoa powder and cocoa butter, you will essentially be reconstituting the original chocolate liquor and then sweetening the mixture with no more than 50 percent sugar if you're aiming for a semi-sweet product.
However, cocoa butter is expensive and unavailable in most grocery stores. You can order it online or find it at specialty shops, or you can substitute a different fat that is solid at room temperature, like butter or coconut oil. If you're really serious about making homemade chocolate, you can buy a tabletop melanger for about the price of a good food processor and grind your own cacao nibs along with sugar to make high-quality chocolate.
Homemade Chocolate and the Tempering Process
When you make chocolate from scratch with a melanger or just melt finished chocolate to make confections like truffles, you'll need to temper the mixture in order to get it to solidify and attain an appealing texture. You can temper the mixture by adding some grated finished chocolate to the new chocolate and by watching the temperature closely because you need the right temperature to get the cocoa butter to form the right kind of crystals.
If you make chocolate from cocoa powder and cocoa butter, you probably won't want to go to the trouble of monitoring the temperature and tempering your chocolate. If you're using an alternate fat, such as coconut oil or butter, the tempering process won't even work because these ingredients simply don't solidify in the same way at the same temperature. If you use a liquid sweetener such as honey or agave syrup, you'll have even more trouble getting your chocolate to set.
Fortunately, you can get around these issues by simply putting your chocolate in the refrigerator or freezer. Freezing will get the job done quickly and efficiently, but you probably won't want to serve your chocolate frozen. Store homemade chocolate in the refrigerator and take it out right before it is time to serve.