If I had to give the Most Underrated Professor Award to anyone I studied under, it would easily have to be Professor Meir Kohn. His work falls squarely outside the paradigm of mainstream economics, which (coming from me anyway) could not be a higher compliment – yet also makes it difficult to get traction inside the field. Kohn himself wrote a great essay contrasting the mainstream paradigm of Samuelson and Hicks with the lineage of more qualitative thinking descended from Adam Smith, including fields like economic history and new institutional economics and public choice theory among others.
He has been working on a theory of economic development for two decades now, and in my opinion it appears to be substantially correct. He first composed an unpublishable opus about European economic development from 1000-1600, which I read in its entirety. Then he wrote a more condensed version, where he applied the theory to China as well as Europe, which is likely going to be published in the next couple of years. In private correspondence, he has indicated that he and his students are now applying the model quite successfully to analyzing other economies throughout history.
The first chapter of his first opus contains the best description of his overall model I have yet read. Because I hold it in high regard, believe it to be fundamentally true, and I refer to it often, I am posting my summary of it below. All errors and omissions are mine.