01 -
Preheat the oven to 375°F (190°C) and butter a baking dish.
02 -
Peel and slice the potatoes thinly, then layer them in the buttered baking dish.
03 -
In a saucepan over medium heat, melt the butter and whisk in the flour. Cook, stirring, until smooth. Gradually add the milk and cream, whisking constantly to avoid lumps. Season with onion powder, garlic powder, salt, and pepper. Bring to a boil, then lower the heat and simmer until thickened, stirring occasionally.
04 -
Add the mozzarella and cheddar cheese to the sauce and stir until completely melted.
05 -
Pour half of the cheese sauce over the layered potatoes and cover the dish with foil. Bake for 30 minutes.
06 -
Remove the foil, pour the remaining sauce over the potatoes, and bake uncovered for another hour or until the potatoes are golden and tender.
07 -
Garnish with parsley or dill and serve hot or warm.