Chicken Broccoli Supreme

My love for chicken and broccoli dishes runs deep y'all.  Real deep. This recipe is adapted from Sugar Spice and Spilled Milk. 

1 large head of broccoli (cut into bite size pieces and lightly steam)
3 chicken breast (cooked and cubed)
1/3 cup butter
1/3 cup flour
1/2 cup chicken broth
1/4 tsp salt
1/4 tsp pepper
2 cups milk
3 cups grated cheddar cheese (divided)
1 sleeve Ritz crackers
4 tbsp butter
1 tablespoon poppy seeds

Heat oven to 350.  Layer the chicken and broccoli in a large baking dish.  In a sauce pan melt butter then whisk in the flour over medium heat.  Lower the heat and whisk in the chicken broth, salt, pepper and milk. Continue to stir. Once the mixture starts to thicken up, whisk in 1 1/2 cups of cheddar cheese and stir until melted. Pour the sauce over the chicken and broccoli. Top with the remaining cheddar and poppy seeds. Crush up the crackers and sprinkle over the top. Cut the butter in small chunks and spread out over the casserole. Bake in the oven for 30 minutes or until it begins to bubble.