Preheat the oven to 350°
Bring a large pot of salted water to a boil. Add in florets and boil for 3-5 minutes, or until bright green and tender. Strain and set aside
Meanwhile, in a saucepot, add butter and diced shallots. Cook for 2 minutes or until the shallots are tender
Sprinkle flour over the shallots, and whisk until no dry flour remains. Continue to cook for 1 minute.
Pour in milk and whisk to combine. Bring to a simmer and allor to thicken, about 5 minutes.
Once the sauce coats a spoon, whisk in mustard and cheese, until cheese is melted and the sauce is smooth. Season with salt and pepper to taste.
Add in broccoli to cheese sauce and mix gently to combine. Pour into a greased casserole dish.
Top with crushed crackers and spray liberally with cooking spray. Bake for 15-20 minutes until crackers are golden brown and the sauce is bubbling. Serve immediately.
