Brush both sides of portabella caps with olive oil, season with salt and pepper and grill approximately 5 minutes per side. Slice and set aside. In a small mixing bowl stir together mayonnaise and hot sauce; set aside.
Portion ground chuck into 6 patties, season with salt and pepper and grill to desired doneness (recommended 160°F internal temperature). Top each with slice of cheese.
To assemble, spread bun bottom with spicy mayo, top with lettuce, burger and mushroom slices. Image and Recipe Courtesy of Certified Angus Beef ® brand