Preheat your oven to 400°F (200°C).

In a large mixing bowl, toss diced potatoes with olive oil, salt, and pepper. Spread on a baking sheet. Bake for about 25-30 minutes, stirring halfway through.

While the potatoes bake, bring a pot of water to a boil. Add broccoli florets and blanch for 3-5 minutes. Drain and plunge into ice water.

In a medium bowl, combine sour cream, milk, garlic powder, onion powder, salt, and pepper. Whisk until smooth.

In a large mixing bowl, combine the baked potatoes, cooked chicken, steamed broccoli, and creamy sauce. Gently fold until well-coated.

Grease a 9x13-inch baking dish. Pour the casserole mixture into the dish and top with shredded cheddar and grated Parmesan cheese.

Bake for 20-25 minutes, or until cheese is melted and golden brown.

Remove from oven and let it rest for 5-10 minutes. Garnish with fresh parsley before serving.