Preheat oven to 350°F (175°C). Lightly grease a 9x13 inch baking dish.
In a large bowl, combine sour cream, heavy cream, cream cheese, garlic powder, salt, and pepper. Mix until smooth.
Add sliced potatoes to the cream mixture and toss to coat.
Pour potato mixture into the prepared baking dish. Spread evenly.
Sprinkle cheddar cheese evenly over the top.
Bake for 50 minutes, or until potatoes are tender and cheese is golden brown and bubbly.
Let stand for 10 minutes before serving.
Notes
This dish can be prepared ahead of time. Assemble the potatoes and cream mixture in the baking dish, cover, and refrigerate for up to 24 hours. Add the cheese just before baking.