Feta Florentine Burgers with Frizzled Prosciutto on Parmesan-Toasted Ciabatta Rolls

INGREDIENTS

• 3/4 cup mayonnaise
• 6 ciabatta rolls, split
• 6 tablespoons freshly grated Parmesan
• 1 1/2 cups thinly sliced fresh spinach leaves
• 1/2 cup finely chopped white onion
• 2 tablespoons oil-packed sun-dried tomatoes, drained and chopped
• 6 slices (1/4-inch thick) fresh mozzarella cheese
• 1/2 cup crumbled feta cheese
• Vegetable oil, for brushing on the grill rack
• 3 cups mesclun greens
• 1 garlic clove, peeled and cut in 1/2 lengthwise
• 4 tablespoons extra-virgin olive oil (recommended: Colavita)
• 1 cup chopped white mushrooms
• 2 tablespoons extra-virgin olive oil (recommended: Colavita)
• 1 1/2 cups thinly sliced prosciutto
• 1/2 cup finely chopped red bell pepper
• 2 teaspoons salt
• 2 1/2 pounds ground sirloin