Great super-flavorful burgers! We cooked these on the grill and did top them with the mushrooms before melting the provolone. I used shredded mozzarella as that's what I had on hand; I just put it on the bottom half of the bun and put the hot burger on top. Finished off with pizza sauce and really enjoyed these - thanks for sharing the recipe!
This is a definite repeat recipe for this family. I got nothing but positive feedback on the great flavor these burgers had. I didn't use the pizza sauce as a topping as DH said he only wanted the usual hamburg condiments. So, he topped his w/yellow mustard, ketchup, and onion w/a slice of sharp cheddar. I should also mention that he did these on the grill. A great idea using the food processor too.