Preheat oven to 350℉.
Bring large pot of water to a boil.
Add broccoli to the boiling water and allow to cook for 1-2 minutes until bright green.
Remove broccoli and place in a bowl filled with ice water.
In a medium size sauce pan melt butter over medium heat.
Whisk in flour, salt, black pepper, onion powder and garlic powder.
Allow to cook for 2-3 minutes while stirring.
Whisk in milk, continue to cook over medium/low heat while whisking until thickened.
Remove from heat and stir in cheddar cheese until melted.
Mix broccoli with cheese sauce and add to casserole baking dish.
Top broccoli with remaining cheddar cheese.
In small bowl combine panko with melted butter. Stir to combine. Then sprinkle over top of broccoli casserole.
Bake for 20 minutes, until heated through and bread crumbs on top are a golden brown color. Serve warm.
