Preheat your oven to 400°F (200°C).

In a large bowl, toss the diced potatoes with olive oil, salt, and black pepper until they are evenly coated.

Spread the potatoes in a single layer on a baking sheet and roast in the preheated oven for about 20-25 minutes, or until they are golden brown and tender.

While the potatoes are roasting, steam or boil the broccoli florets just until tender, about 4-5 minutes. Drain and set aside.

In a saucepan over medium heat, melt the butter. Add the shredded or diced chicken, stirring occasionally until heated through.

In a separate mixing bowl, combine the sour cream, milk, garlic powder, onion powder, and half of the cheddar cheese.

In a large casserole dish, layer the roasted potatoes, then the cooked chicken and broccoli.

Pour the sour cream mixture over the top and gently stir to combine all ingredients evenly.

Sprinkle the remaining cheddar cheese and grated Parmesan cheese over the top.

Reduce the oven temperature to 350°F (175°C) and bake the casserole for an additional 20-25 minutes, or until the cheese is melted and bubbly.

Remove from the oven and let it sit for about 5 minutes before serving.

Garnish with fresh parsley if desired.