I teach in a university to Masters students in Science. I have taught courses from Physics, Statistics, Mathematics and Computation, and every time I finish teaching a course, I find myself unsatisfied. It is difficult to articulate what exactly I feel unsatisfied with, but it is probably a combination of choice of topics, the order in which I taught them, the total amount of depth I covered each topic to, the way I explained the concept, the type of problems I assigned for practice, the way I gave my feedback to student submissions etc. One thing that I always seem to fear while teaching is that even if I explained something, students may not have understood it. This makes me extremely conscious during the class itself, and once I start thinking about it while I am talking, I seem to forget things, which in turn leads to fumbling, and that feeling is disturbing.
Over the years, I have made active efforts to improve. However as the courses that I teach seem to become more and more difficult as I progress in my career, the improvement seems to be lagging quite a lot. During my bachelor's degree, I had devoured Feynman Lectures on Physics, and that motivated me a lot to become a good teacher. Even now while reading these, I "hear" the sentences in Feynman's voice with all ups and downs of the tone. I have also read the book "The craft of scientific presentations" by Michael Ally, and several other articles. Perhaps it is needless to say that I have tried to implement various strategies learned from these resources into my teaching. However, I still feel that my teaching is not up to the mark. When I think of some of the scientists I personally know, their teaching seems flawless (I have attended their actual in-person courses). Here I am not saying that each one of them mesmerize the students in the class, but that given their styles, everything seems to fall in place when they are teaching. Let it be a difficult calculation, or a complex explanation of conceptually difficult concept, they seem to get it done as if it is a piece of cake.
Given this, I am looking for books or other resources that specifically talk about great teachers and their teaching methods, especially in advanced science. The books should not cover just some algorithms which should be followed but they should emphasize how teaching can be approached as an art that can be learned and excelled. Two good books (about different topics) which are of this type are "Writing Science" by Joshua Schimel, and "Craft of Scientific Presentations" by Michael Ally.