Preheat oven to 400 degrees F. In a medium sized saucepan, bring heavy cream, salt, garlic powder, onion powder and pepper to a simmer and cook for 3 to 5 minutes, until slightly thickened. Remove from heat and stir in potatoes and let sit while you grate the cheeses.
Lightly oil a cast iron skillet or 8x8 baking dish. Layer half the potatoes into the skillet, leaving as much cream in the saucepan as possible. Sprinkle half the cheese over the layered potatoes. Layer remaining potatoes over the cheese. Pour cream left in saucepan evenly over the potatoes. Top with remaining cheese.
Cover lightly with foil and bake for 40 minutes. Remove foil and bake another 30 minutes uncovered or until potatoes are tender when poked. Sprinkle with parsley after removing from oven.