Ground Beef and Rice Casserole

Bahan-bahan (6 porsi)

• 1 pound lean ground beef
• 1 onion (diced)
• 8 ounces canned sliced mushrooms (1 can, drained)
• 1 clove garlic (minced)
• ½ teaspoon dried oregano
• 10 ounces frozen chopped spinach (1 package, thawed and squeezed dry)
• 1 cup instant rice
• 1 ¼ cup water
• 10.5 ounces condensed cream of celery soup (condensed)
• ⅓ cup sour cream
• salt and pepper to taste
• 1 cup shredded mozzarella cheese
• ½ cup frozen mixed vegetables