01 -
Preheat the oven to 190°C (gas mark 5) and generously butter a baking dish.
02 -
Peel potatoes if desired. Using a sharp knife or mandolin, slice potatoes thinly and evenly.
03 -
Layer the thinly sliced potatoes in the prepared baking dish as preferred—standing upright or laying flat.
04 -
Melt butter in a saucepan over medium heat. Whisk in flour and cook, stirring constantly, until smooth. Gradually add milk and cream, whisking to avoid lumps. Season with onion powder, garlic powder, salt, and black pepper. Bring to a gentle boil, then simmer, stirring occasionally, until thickened.
05 -
Stir mozzarella and cheddar cheese into the sauce until fully melted and the sauce is smooth.
06 -
Pour half of the cheese sauce over the potatoes, ensuring even coverage. Cover the dish tightly with foil and bake for 30 minutes.
07 -
Remove foil and pour the remaining cheese sauce evenly over the potatoes. Return to the oven and bake, uncovered, for approximately 60 minutes or until the top is golden and potatoes are tender.
08 -
Sprinkle with chopped parsley or dill before serving. Serve hot or warm alongside your preferred main dish.