Bring a few inches of water to a simmer in a saucepan. Place a steamer basket in the pan and add your broccoli. Top with a lid and steam until it reaches desired tenderness.
Meanwhile, make the cheese sauce. Heat a small saucepan over medium heat. Add butter and allow to melt. Sprinkle in flour, salt, pepper and garlic powder. Whisk well and cook for 2 minutes, whisking often. Add milk to the flour mixture and whisk well until smooth. Bring to a simmer, whisking constantly, until the sauce has thickened enough to nicely coat the back of a spoon. Add shredded cheese and whisk until melted.
Drizzle broccoli with desired amount of cheese sauce.