Healthier Broccoli Chicken Casserole

Bahan-bahan (6 porsi)

• 8 ounces uncooked pasta* (I used whole-wheat rotini)
• 1 large head of broccoli*, cut into bite-sized florets (about 1 pound of florets)
• 2 tablespoons butter or olive oil
• 1 small white onion, thinly sliced
• 8 ounces baby bella (cremini) mushrooms, thinly sliced
• 4 cloves garlic, minced
• 3 tablespoons flour
• 1 cup chicken or vegetable stock
• 1 1/2 cups milk
• 1 teaspoon Dijon mustard
• 1/2 teaspoon fine sea salt
• 1/4 teaspoon freshly-cracked black pepper
• 2 cups (8 ounces) shredded sharp cheddar cheese, divided
• 2 cups diced (or shredded) cooked chicken