Ingredients

• 2 1/2 pounds ground sirloin beef
• 1 cup fresh or store-bought pesto, recipe follows
• 1/4 cup grated Parmesan
• 1 1/2 teaspoons kosher salt
• 1/2 teaspoon freshly ground black pepper
• One 7 to 8-ounce ball fresh mozzarella, sliced into eight 1/4-inch-thick slices, patted dry with paper towels
• 1/2 cup mayonnaise
• 1/4 cup fresh or store-bought pesto
• Extra-virgin olive oil for drizzling
• Eight 3-inch-square pieces of tomato or plain focaccia bread, halved, or 8 hamburger buns, halved
• 4 medium tomatoes, sliced into 1/4-inch-thick rounds (16 slices)
• 2 packed cups fresh basil leaves
• 1 cup grated Parmesan
• 1/4 cup pine nuts, toasted
• 1/2 teaspoon kosher salt
• 1/4 teaspoon freshly ground black pepper
• 2 cloves garlic, smashed
• 1/4 cup extra-virgin olive oil

Instructions

1. Watch how to make this recipe.
2. For the burgers: Place a grill pan over medium-high heat or preheat a gas or charcoal grill. Combine the beef, pesto, Parmesan, salt and pepper in a large bowl. Form the mixture into eight 4-inch-diameter patties, each about 3/4-inch thick. Grill for 5 minutes. Turn the burgers over and place a slice of mozzarella on top. Cook for about 5 minutes longer until the burgers are cooked through and the cheese is slightly melted. Allow the burgers to rest for 5 minutes.
3. For the pesto mayonnaise: In a small bowl, combine the mayonnaise and pesto until smooth.
4. To assemble the burgers: Drizzle the cut side of the bread with olive oil and grill until lightly toasted, 1 to 2 minutes. Spread the pesto mayonnaise over the bottom halves of the grilled bread. Place the burgers on top and add 2 tomato slices. Add the top halves of the bread and serve.
5. Bake in a preheated 350 degrees F oven until lightly toasted, 6 to 8 minutes. Cool completely before using. Combine the basil, Parmesan, pine nuts, salt, pepper and garlic in a food processor. Pulse until finely chopped. With the machine running, gradually add the olive oil until the mixture forms a smooth paste.