Grass fed buffalo is so lean that the only way that burger would be juicy is be to stuff it full of cheese. The "fermenting" of the beef probably just keeps if from being the consistency of dried out leather. The onions were certainly nicely caramelized - 40 minutes to do them is about right.
But, meh. I doubt that's a great burger. You can make pretty bad food look good on film and you can just as easily take 30 days to make food that's every bit as bad as you can make in 30 minutes.