Preheat the Oven: Start by preheating your oven to 350°F (175°C).
Prepare the Potatoes: Peel and cube the russet potatoes. Bring a large pot of salted water to boil and add in the potatoes. Cook them for about 15-20 minutes, or until tender. Drain and set aside.
Mix the Cheese Sauce: In a large bowl, combine the sour cream, melted butter, milk, garlic powder, onion powder, salt, and pepper. Stir in 1 ½ cups of the shredded cheddar cheese, reserving the remaining cheese for topping.
Combine: Gently fold the cooked potatoes into the cheese mixture, ensuring each piece is well coated.
Layer the Dish: Transfer the potato mixture into a greased 9x13 baking dish. Spread it evenly and top with the reserved cheese.
Bake: Bake in the preheated oven for about 25-30 minutes or until the top is bubbly and golden brown.
Serve: Remove from the oven and let it cool slightly before serving. Don’t forget to garnish with optional green onions or crispy fried onions for extra texture!