FOR THE RED PEPPER KETCHUP:
¼ cup ketchup
1 (12-ounce) jar roasted red peppers
FOR THE PESTO MAYO:
½ cup mayonnaise
2 tablespoons pesto
FOR THE BURGERS:
2 cups frozen chopped onions
5 tablespoons canola oil
1½ pounds ground beef, 85 percent lean
2 tablespoons grill seasoning
¼ pound blue cheese, sliced into 4 pieces
2 slices cheddar cheese, each piece cut into 4
2 slices mounceszarella cheese, each piece cut into 4
12 small dinner potato rolls, sliced in half and toasted
TO MAKE RED PEPPER KETCHUP:
In a mini chopper or blender, combine ketchup and roasted red peppers (reserve one red pepper to garnish the burgers). Blend until smooth. Set aside.
TO MAKE PESTO MAYO:
Combine mayonnaise and pesto in a small bowl and stir together. Set aside.
TO MAKE BURGERS:
Heat 3 tablespoons of oil in a large pan over medium-low heat. Add onion and cook until caramelized, about 15 to 20 minutes, making sure to stir every few minutes.
Form the ground beef into 12 equal-sized mini patties. Heat the remaining oil in a large skillet over medium-high heat. Season both sides of each patty with the grill seasoning and place into the skillet. Cook for 3 minutes. Flip the burgers, top four with the blue cheese, the next four with 2 slices of cheddar cheese each, and the final four with 2 slices of mounceszarella cheese each. Cover with a lid and cook for another 2 to 3 minutes until cheese is melted.
Place the burgers onto the bottom half of each roll. Top the blue-cheese burgers with the caramelized onion then with the top of the roll. Slice the reserved red pepper into 4 pieces. Top the cheddar burgers with roasted red pepper pieces, roasted red pepper ketchup, and the top of the roll. Finally, top the mounceszarella burgers with the pesto mayo and the top half of the roll.