Types of Baking Cocoa
When recipes call for "cocoa," use unsweetened baking cocoa, not hot chocolate mix products which are sweetened and have additional ingredients. Two types of baking cocoa are available: nonalkalized (regular) and alkalized ("Dutch" or "European"). Alkalized cocoa goes through a "Dutching" process to neutralize natural acids found in cocoa. The result is a darker cocoa with a mellower chocolate flavor than regular cocoa. The two types of cocoa can be used interchangeably, but baked goods made with Dutch cocoa will be darker in color and be a bit milder in flavor.
Perfectly melted chocolate, like in the first bowl, is smooth and creamy.
If chocolate has been melted over too high a heat or has come in contact with a small amount of liquid, it can tighten, or become seized, as seen in the second bowl.
To make seized chocolate smooth and creamy again, use a whisk to or beat in at least 1 tablespoon melted butter, vegetable oil or melted vegetable shortening. Heat over very low heat, if necessary, stirring constantly. The result will look like the third bowl.