Wow, one fine burger Al. Add a few sauteed mushroom next time on mine!
I like mushrooms, but not on the perfect cheeseburger. Dilutes the flavor of the meat, cheese, onion and pickle. Maybe on the side. Choices for me are mustard? or mayo, or both? I even like miracle whip!. Good slice of beefsteak tomato also is good, esp with mayo. I think when you use mushrooms, then sautéed onions and mayo go well with it. Avocado IMO has a negative flavor effect on a good burger, but again on the side is ok. Bacon, on the other hand is good on anything!.
Yes I am opinionated--!