Me and my roommate want to make a batch of brownies, however each of us has their heart set on a different recipe: I want to use one from Serious Eats because it's loaded with cocoa and I have a lot of faith in that site; he wants to use one that uses beetroot because he thinks it's healthier and someone gave him a few that we need to use up. (I thoroughly despise beets but I'm hoping that enough cocoa will cover them up here.)
Is there a way to get the best of both worlds? I've done cakes with shredded carrot and/or apples, and I assume the vegetables mostly contribute liquid and some structure. Is there some general rule I can use to replace some of the ingredients in a cake batter recipe for shredded beetroot other than trial and error?