Broccoli and Mushroom Casserole
Preheat oven to 350°. Grease 13x9 baking dish with cooking spray. Set aside.
In a large saucepan, heat oil over medium/high heat. Add onions and celery and cook until softened (about 5 minutes). Add mushrooms and cook another 5 minutes. Sprinkle flour over vegetables and cook an additional minute. Add stock and stir scraping up bits from bottom of pot as you stir (about 3 minutes).
Remove from heat and add milk, yogurt, salt and pepper. Add Broccoli and 1/2 the cheese. Pour mixture into a baking dish.
In a small bowl mix the remaining cheese with the cracker crumbs. Sprinkle on top of mixture in the baking dish. Bake for 30 minutes.