Pizza Sandwiches Supreme

Ingredients

• 1/2 pound ground beef
• 1/4 cup Parmesan cheese, grated
• 1/4 cup ripe olives, chopped
• 1, 6 ounce can tomato paste
• 2 tablespoons chives, chopped
• 3/4 teaspoon salt
• 1/4 teaspoon oregano
• 1/8 teaspoon pepper
• 3 hamburger buns, split
• 2 slices Mozzarella cheese, cut in thirds