To Prepare the Caramelized Onion and Blue Cheese Spread:
Place cream cheese in a food processor and puree until smooth, scraping the sides and blade often. Add caramelized onions, mayo, blue cheese, thyme and black pepper. Pulse until well incorporated, scraping often. Season with salt to taste.
To Prepare the Burgers:
Allow the burgers to sit out on a plate for 15 minutes to temper. Season the burgers with salt and pepper and grill them over high heat around 3 minutes per side or desired internal temperature is reached. While burgers are being grilled, place buns over medium low heat on a separate burner and toast slightly. Serve burgers with blue cheese spread - add bacon, lettuce and tomato as desired.