Preheat oven to 375˚F.
Lightly spray a 3-quart baking dish with cooking oil and set aside.
Bring a large pot of water to a boil.
Add broccoli to boiling water and cook for 2 minutes.
Drain the broccoli; rinse with cold water until completely cooled.Transfer broccoli back to the pot where you cooked the broccoli. Set aside.
Melt butter in a large saucepan set over medium heat.
Whisk in the flour to combine; cook for 2 minutes.
Slowly whisk in the Half & Half; cook and whisk until the mixture starts to thicken.
Remove from heat and whisk in the gruyere cheese, ½ cup feta, garlic powder, salt, and pepper. Whisk and stir until it's completely combined and melted.
Pour the cheese sauce over the broccoli; add in the crumbled bacon, and toss to coat.
Transfer broccoli to previously prepared baking dish; sprinkle with remaining feta, and set aside.
In a mixing bowl stir together melted butter, crumbs, salt, pepper, and chives.
Sprinkle over the broccoli.
Bake for 25 to 30 minutes, or until top is browned and mixture is bubbly.
Remove from oven and let stand 5 minutes before serving.