Hamburger Rice Casserole

Ingredients

• 1 tablespoon butter
• 1 pound ground beef
• 1/2 medium onion, chopped
• 2 garlic cloves, minced
• 1 teaspoon dried oregano
• 1 teaspoon salt
• 1/2 teaspoon pepper
• 2 cups uncooked instant rice
• 1-1/2 cups reduced-sodium beef broth
• 1 can (15 ounces) crushed tomatoes
• 1 can (10-1/2 ounces) condensed cream of mushroom soup, undiluted
• 2 teaspoons Worcestershire sauce
• 1 cup shredded cheddar cheese, divided
• 1/4 cup chopped dill pickle
• 1 tablespoon prepared mustard