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

Bring a large pot of salted water to a boil, add the green beans and potatoes, and cook for 8 minutes until tender-crisp. Drain and set aside.

In a skillet over medium heat, warm olive oil, add chopped onion, and sauté for 3 minutes. Stir in minced garlic and cook for 1 more minute.

In a large mixing bowl, combine sour cream, heavy cream, shredded cheddar cheese, grated parmesan, paprika, black pepper, and salt. Fold in sautéed onion and garlic.

Add the parboiled green beans and potatoes to the creamy mixture, toss to coat, then transfer to the greased baking dish.

Combine breadcrumbs with melted butter in a bowl and sprinkle over the casserole evenly.

Bake for 25-30 minutes until the top is golden brown and bubbling. Watch closely towards the end.

Let the casserole rest for a few minutes before serving. Garnish with fresh parsley.