Preheat your oven to 375°F (190°C). Lightly grease a 9x13 inch baking dish.

Bring a large pot of salted water to a boil. Add the trimmed and cut asparagus pieces and blanch for 2-3 minutes, until bright green and slightly tender-crisp. Drain immediately and transfer to an ice bath to stop the cooking (this helps retain color and texture). Once cooled, drain well and pat dry. Toss the asparagus with olive oil in a bowl.

In a large skillet or saucepan, melt the butter over medium heat. Add the all-purpose flour and whisk constantly for 1-2 minutes to create a roux, cooking out the raw flour taste.

Gradually whisk in the milk and heavy cream until smooth. Bring the mixture to a gentle simmer, whisking frequently, and cook for 3-5 minutes until the sauce thickens.

Remove the skillet from the heat. Stir in the salt, black pepper, and garlic powder. Add 6 ounces of the shredded cheddar cheese, all of the cream cheese, and all of the Parmesan cheese. Stir until all the cheeses are melted and the sauce is smooth and creamy.

Add the blanched asparagus to the cheese sauce and gently stir to combine, ensuring all the asparagus is coated.

Pour the asparagus and sauce mixture into the prepared baking dish, spreading it evenly.

Sprinkle the remaining 2 ounces of shredded cheddar cheese over the top of the casserole.

In a small bowl, combine the breadcrumbs and melted butter. Sprinkle this mixture evenly over the top of the casserole.

Bake for 20-25 minutes, or until the casserole is bubbly around the edges and the topping is golden brown.

Remove from the oven and let it rest for 5-10 minutes before serving. This helps the casserole set slightly.