Preheat the oven to 400°F (200°C).
Scrub the russet potatoes and prick them several times with a fork. Rub each potato with 1 tablespoon olive oil and sprinkle with 1/2 teaspoon salt.
Place the potatoes directly on the oven rack and bake for 45-50 minutes, or until tender when pierced with a fork.
Remove the potatoes from the oven and let them cool slightly until they can be handled safely.
Reduce the oven temperature to 350°F (175°C).
Cut each potato in half lengthwise and carefully scoop out the flesh into a large mixing bowl, leaving a thin shell to maintain the shape.
Add the butter, sour cream, whole milk, garlic powder, onion powder, smoked paprika, remaining 1/2 teaspoon salt, and 1/4 teaspoon black pepper to the potato flesh. Mash until smooth and creamy.
Stir in the shredded chicken, 1/2 cup shredded cheddar cheese, chopped green onions, and cooked bacon bits until well combined.
Spoon the potato and chicken mixture back into the potato shells, dividing evenly.
Place the stuffed potato halves in a greased 9×13-inch casserole dish.
Sprinkle the remaining 1/2 cup cheddar cheese and 1/2 cup mozzarella cheese evenly over the filled potatoes.
Bake the casserole at 350°F (175°C) for 20 minutes, or until the cheese is melted and bubbly and the casserole is heated through.
Remove from the oven and garnish with chopped fresh parsley before serving.