Preheat oven to 450°F. Steam or boil the broccoli for 5 minutes until crisp-tender. Drain and transfer to a 9-inch pie plate or baking dish.
Top the broccoli with the cooked chicken.
In a bowl, mix together the condensed soup and milk until smooth. Pour over the chicken and broccoli.
Sprinkle the cheddar cheese over top of the sauce.
In a small bowl, mix together the breadcrumbs and melted butter until combined. Sprinkle over the cheese.
Bake for 15 minutes until hot, bubbly, and golden brown on top.
Let cool 5 minutes before serving.