French Onion Soup With an Italian Attitude

Ingridients of French Onion Soup With an Italian Attitude:

• 1 tablespoon extra virgin olive oil
• 2 tablespoons butter
• 6 medium onions , thinly sliced
• salt
• black pepper
• 1 sprig rosemary , leaves removed and finely chopped
• 1/2 pint grape tomatoes , halved
• 1/2 cup fresh basil , torn into pieces (about 10 leaves)
• 1/4 cup shredded parmigiano-reggiano cheese
• 4 thick slices crusty bread
• 1 garlic clove , crushed
• 1 tablespoon balsamic vinegar
• 1/2 cup white wine
• 6 cups beef stock
• 8 slices fresh mozzarella cheese