Step 1

Preheat the oven to 375° and spray a 9x13 inch casserole dish with non-stick cooking spray.

Step 2

In a large pot, add an inch of water and heat to simmering.  Add the broccoli and place a lid on the pot. Steam the broccoli for 4 minutes or until the broccoli turns a bright green. Remove from the pan immediately and set aside.

Step 3

In a large saute pan, melt 2 Tablespoons of butter and cook the onion, celery, and garlic for 4 minutes.

Step 4

Add the soup, milk, mayonnaise, sour cream, worcestershire sauce, mustard powder, salt, pepper, and 1 cup of the cheese. Stir and cook until the cheese has melted and everything is well-combined.

Step 5

Stir in the broccoli and chicken and transfer to the baking dish.

Step 6

Top with remaining cheese. Melt the remaining butter and stir into the panko. Sprinkle the panko topping evenly over the top of the casserole.

Step 7

Bake for 25 minutes or until bubbly and the cheese has melted.

Step 8

Serve warm and enjoy.