A healthier twist on the classic potato gratin, perfect for a comforting yet light meal.
Preheat your oven to 375°F and coat a 2-quart baking dish with cooking spray.
Ensure the oven is fully preheated for even cooking.
Melt the butter in a large frypan over medium heat. Add the diced onion and sauté until it softens and begins to brown, about 5 minutes.
Stir frequently to prevent the onion from burning.
Sprinkle the flour over the onions and stir to combine. Gradually whisk in the milk, ensuring no lumps form.
Adding the milk slowly helps create a smooth sauce.
Add the sliced potatoes to the sauce, stirring to coat them evenly. Bring the mixture to a gentle boil.
Slice the potatoes thinly for quicker cooking.
Stir in half of the cheese, along with the salt and black pepper. Mix well.
Taste the sauce and adjust seasoning if needed.
Pour the potato mixture into the prepared baking dish, spreading it out evenly.
Ensure the potatoes are submerged in the sauce for even cooking.
Bake uncovered for 1 hour. Then cover with foil and bake for an additional 20 minutes.
Covering the dish prevents the top from over-browning.
Switch the oven to broil. Sprinkle the remaining cheese over the top and broil until golden, about 1-2 minutes.
Keep an eye on the broiler to avoid burning the cheese.
Let the gratin cool for 5 minutes before serving.
Cooling allows the sauce to set for easier serving.
