Does it matter whether the cocoa I use is called Dutch process?
Yes—be sure to follow recipe instructions when it comes to using “Dutch process” or “natural” cocoa. Dutch process cocoa is milder tasting and deep brown because it has been treated with an alkali whch helps neutralize the cocoa's natural acidity. Natural cocoa has not been treated with an alkali and has a reddish cast.
If you use Dutch process when natural cocoa is required, your cake may end up with a soapy flavor, and the texture can be greatly affected. (The cake may not rise or set). Cookies made with natural cocoa will spread less than those made with Dutch process.
This recipe for Dutch-Chocolate Angel Cake is a great use of Dutch process cocoa.