MAKE BALSAMIC REDUCTION: Add ½ cup good balsamic vinegar to a small saucepan over medium heat. Bring to a gentle boil, then reduce heat to medium-low. Simmer for 6 to 8 minutes until the vinegar reduces by about half and becomes slightly syrupy. Remove from heat and set aside to cool. The sauce will thicken as it cools.

PREHEAT GRILL: Preheat a grill to medium-high heat, about 400°F.

FORM PATTIES: Place 1 ½ pounds 80 to 85 percent lean ground beef in a large bowl and gently divide into 4 equal portions. Shape each portion into a patty slightly larger than the ciabatta buns. Press a shallow indentation into the center of each patty so the burgers cook evenly.

SEASON BURGERS: Sprinkle the patties evenly with 1 teaspoon kosher salt and ½ teaspoon fresh ground black pepper on both sides.

GRILL BURGERS: Place the patties on the grill and cook for 3 to 4 minutes until a browned crust forms. Flip the burgers and cook another 3 to 4 minutes for medium doneness, until the internal temperature reaches about 160°F.

ADD CHEESE: During the last minute of cooking, place 1 slice of 4 ounces fresh mozzarella cheese, sliced into 4 slices on each burger. Close the grill lid so the cheese melts.

TOAST BUNS: Place 4 ciabatta buns, split cut side down on the grill and toast for about 30 to 60 seconds until lightly golden.

MAKE PESTO MAYO: In a small bowl stir together ½ cup prepared pesto and 3 tablespoons olive oil mayonnaise until smooth.

ASSEMBLE BURGERS: Spoon about ¼ cup of the 1 cup chunky tomato sauce onto the bottom half of each bun. Place the cheeseburger on top. Drizzle a little balsamic reduction over the cheese. Spread about 2 tablespoons pesto mayo on the top bun and place it over the burger.

SERVE: Serve immediately while the burgers are warm and the cheese is melted.