A quick note: There are some questions that can’t be asked because they make no sense. Posing the question seems to lend legitimacy to the underlying assumptions, when the premise of the question is false to begin with.
I think this is true of our questions regarding the existence of free will and the cause of consciousness. As choice and the experience of choice are processes of the brain, asking how mental events can control brain processes is just asking how one brain process can lead to another brain process. It’s really not a useful question.
While in some sense it may be a category error, trying to combine two categories into one question, it seems more just based on an illusion from introspection, much like asking how does the sun go around the earth when really we know that the earth rotates. It’s the question that’s at fault, not some missing stuff that makes up the “qualia”.