Italian Spaghetti Squash Casserole - Slender Kitchen

Ingredients

• 1 spaghetti squash (large)
• 1 tbsp olive oil
• 1/2 onion, minced
• 1 carrot, diced
• 1 celery stalk, diced
• 4 garlic cloves, minced
• 1 lb 95% lean ground beef
• 16 oz. crushed tomatoes (ideally San Marzano)
• 2 tbsp. tomato paste
• 1 tsp. Italian seasoning
• 1 bay leaf
• 4 cups spinach
• 4 oz. fresh mozzarella
• Salt and pepper