This is an ultra-Dutch processed cocoa powder. All the acidity has been neutralized, rendering the cocoa powder completely mellow, non-bitter, and very black. Think of black cocoa powder almost as more of a coloring ingredient than a flavoring one—it will turn your baked goods as deeply black as you could ever hope for.
Because it's been so heavily Dutch processed, this cocoa powder presents some challenges when baking. It contains almost no fat, which can make baked goods dry and crumbly. You can either use half black cocoa and half regular Dutch-processed cocoa in your recipe, or you can up the fat a little bit.
Black cocoa also contains no acid, it won't react with baking soda. Be sure to use baking powder instead, substituting one teaspoon of powder for every 1/4 teaspoon of soda called for in the recipe.
If you're having trouble finding black cocoa powder, you can also try Hershey's Special Dark Cocoa. It's not quite as "Dutched" as black cocoa, but will get you closer to your goal than other cocoa powders.
Have you ever baked with black cocoa powder?
(Images: King Arthur Flour)