HiCustomer and welcome back to Just Answer!

My name is XXXXX XXXXX being an avid home cook and baker, I would be glad to help you with your question today!

If you would like to make the color of the entire cheesecake brown throughout, and want it to have a chocolate flavor, you can make a 'chocolate cheesecake' with the recipes listed below:

http://allrecipes.com/recipe/chocolate-cheesecake/ (as you can see the brown color and chocolate flavor in this one are achieved by adding melted chocolated chips to the recipe)

In the following recipes, both melted chocolate and unsweetened cocoa powder are used:

http://www.foodnetwork.com/recipes/anne-thornton/deepest-darkest-chocolate-cheesecake-recipe/index.html

http://www.foodnetwork.com/recipes/emeril-lagasse/seriously-chocolaty-cheesecake-recipe/index.html

http://www.foodnetwork.com/recipes/nigella-lawson/chocolate-cheesecake-recipe/index.html

Adding cocoa and using the same amount of flour resulted in an excess of dry ingredients and that's why your cheesecake came out too dry. When adding ingredients not included in an original recipe, it's necessary to adjust the amounts of other ingredients to get a wonderful finished product.

Here is some interesting information about the two types of unsweetened cocoa powder available: http://www.joyofbaking.com/cocoa.html

In most conventional chocolate cheesecake recipes, unsweetened cocoa powder cannot be substituted for the flour, because they consist of different ingredients. As you can see in the link above, cocoa powder is made when chocolate liquor is pressed to remove three quarters of its cocoa butter, then, the remaining cocoa solids are processed to make a fine, unsweetened cocoa powder. All Purpose flour is a combination grind of a hard and soft wheat.

Here is a recipe for a flourless chocolate cheesecake, using cocoa powder:
http://www.celiac.com/articles/888/1/Chocolate-Cheesecake-Gluten-Free/Page1.html

I hope you make a terrific chocolate cheesecake and enjoy!

If you need any additional information, please click 'Reply' and direct your response to me, 'Cher'.

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Best regards,
Cher