Preheat your oven to 400°F (200°C).
Wash and peel the potatoes. Cut them into bite-sized cubes.
In a large mixing bowl, combine the sour cream, ranch dressing mix, milk, olive oil, garlic powder, black pepper, and salt. Mix until well combined.
Add the cubed potatoes to the mixture and stir until all the potatoes are evenly coated.
Transfer the coated potatoes into a greased baking dish. Spread them out evenly.
Cover the baking dish with aluminum foil and bake in the preheated oven for 30 minutes.
After 30 minutes, remove the foil and sprinkle the shredded cheddar cheese over the top of the potatoes.
Return to the oven and bake uncovered for an additional 15 minutes, or until the cheese is melted and bubbly, and the potatoes are tender when pierced with a fork.
Remove from the oven and let cool for a few minutes. Garnish with fresh chives or parsley if desired before serving.