In a medium bowl, combine the cooked broccoli, shredded cheddar cheese, melted butter, flour, milk, salt, pepper, garlic powder, and onion powder. Mix until all ingredients are evenly combined.
Pour the mixture into a greased 9x13 inch baking dish.
Sprinkle the panko breadcrumbs evenly over the top of the casserole.
Bake in preheated oven for 25-30 minutes, or until top is lightly browned and casserole is bubbly.
Remove from oven and let cool for 5-10 minutes before serving.
Interesting Facts
This dish can be served as a main course or as a side dish.
This casserole reheats well and can be stored in the refrigerator for up to 3 days.
This dish can be easily adapted to include different vegetables, such as chopped bell peppers, mushrooms, or squash.