BURGERS: COMBINE all ingredients, except mushrooms, dressing, rolls and cheddar cheese. Shape into 16 (8-oz.) patties (or eight patties for trial recipe), each about 4 inches in diameter. Cook patties in saute pan (or on flat-top grill) 1 to 2 min. on each side or until browned on both sides. Transfer to two parchment paper-lined full-sheet pans (or to half-sheet pan for trial recipe).
BAKE in 350ºF-convection oven 8 to 10 min. or until burgers reach an internal temperature of 150ºF. Remove from oven. (Temperature will rise to 160ºF as sandwiches are assembled.)
MEANWHILE, marinate mushroom caps in dressing 10 min.; drain. Grill on medium-high heat 6 min. on each side or until tender. Cover to keep warm.
MAYO Mixture: Mix all ingredients until well blended; cover. Refrigerate until ready to use.
BRUSCHETTA Mixture: Combine all ingredients; cover. Refrigerate until ready to use.
FOR each serving: Spread 1 Tbsp. Mayo Mixture onto cut side of one of the roll halves; top with mushroom, burger, cheese slice and 1 rounded Tbsp. of the Bruschetta Mixture. Serve with 5 Polenta Fries.