There are things to be known about cocoa. It goes without saying that baking does not concern itself with the kind of chocolate / cocoa mixes used to make hot chocolate. Cocoa powder for cooking comes in two forms - natural, unsweetened cocoa and Dutch-processed. The photo here shows that the Dutch processed is darker and is often used in cases where the recipe is aiming for a deeper, richer colour and flavour.
David Lebovitz - that fabulous creator of food, who enviably lives in Paris, explains it all in detailed clarity. Worth reading, and a visit to his site might be a little "rabbit hole" adventure as you explore his blog entries and wonderful recipes. In brief:
- remember there IS a difference, and use what the recipe calls for
- some sources say if the recipe calls for Dutch-process you can substitute natural cocoa powder, BUT not vice versa (yet as I noted on the Chocolate Cheesecake Cupcake recipe, I have been doing that for years with no poor outcome...)
- cocoa typically found on grocery store shelves is natural unsweetened
- common brands of Dutch-processed are VanHouten, Droste
Here's another informative update from Food Bloggers Canada's Kitchen Geekery. While I report above having a preference for Dutch-processed, but not noticing a difference, turns out that because of the alkalinity of the two cocoas - and the other ingredients in a cake recipe - the wrong combo can make a difference in the cake's rise.