Portobello Mushrooms with Mediterranean Stuffing

INGREDIENTS

• 4 (4-inch) portobello caps (about 3/4 pound)
• 1/4 cup finely chopped onion
• 1/4 cup finely chopped celery
• 1/4 cup finely chopped carrot
• 1/4 cup finely chopped red bell pepper
• 1/4 cup finely chopped green bell pepper
• 1/4 teaspoon dried Italian seasoning
• 2 garlic cloves, minced
• Cooking spray
• 3 cups (1/4-inch) cubed French bread, toasted
• 1/2 cup vegetable broth
• 1/2 cup (2 ounces) feta cheese, crumbled
• 3 tablespoons low-fat balsamic vinaigrette, divided
• 4 teaspoons grated fresh Parmesan cheese
• 1/4 teaspoon black pepper
• 4 cups mixed salad greens