Combine ground chuck, mushrooms, onion, basil, vinegar and salt. Shape mixture into 4 patties. Grill over med-high heat, for 6 minutes per side, or until internal temperature reaches 160˚. Top each patty with cheese.
To make Pesto Mayo: Combine mayonnaise and pesto. Spread desired amount over each bun. Top with patty, lettuce, and tomato.
Recipe by The eMeals Blog at http://blog.emeals.com/memorial-day-bruschetta-burgers/