Directions
1. Preheat the Oven:
Preheat your oven to 375°F (190°C). Lightly grease a medium-sized baking dish with butter or nonstick spray to prevent sticking and ensure easy serving later. Preparing the dish ahead helps the potatoes bake evenly and allows the sauce to bubble beautifully without clinging to the sides.
2. Prepare the Cheese Sauce:
In a medium saucepan, melt the butter over medium heat. Once melted, add the finely chopped onion and sauté for about 2–3 minutes until soft and translucent. Stir frequently to avoid browning — the goal is to develop a gentle sweetness and aroma from the onion, which adds depth to the sauce.
Sprinkle in the all-purpose flour and stir continuously for about 1 minute to form a smooth roux. This step thickens the sauce later while keeping it creamy and lump-free. Gradually pour in the milk (or cream) while whisking constantly to create a smooth base. Continue whisking over medium heat until the mixture begins to thicken and coat the back of a spoon — about 3–4 minutes.
3. Add the Cheese and Seasoning:
Reduce the heat to low and add the shredded cheddar and mozzarella cheeses, stirring until fully melted and smooth. The cheddar gives the sauce its signature golden hue and tangy flavor, while mozzarella adds stretchiness and creaminess. Season with salt, black pepper, and a touch of paprika for subtle warmth and color. Taste and adjust seasoning if needed before removing the pan from the heat.
4. Assemble the Bake:
Arrange half of the sliced potatoes evenly in the prepared baking dish, overlapping slightly for even cooking. Pour half of the warm cheese sauce over the top, spreading it gently to cover the potatoes. Repeat with the remaining potato slices and pour over the rest of the sauce, ensuring all layers are well coated. The sauce will seep down between the layers as it bakes, creating a luxuriously creamy texture throughout.
5. Bake to Perfection:
Place the dish in the preheated oven and bake for 40–45 minutes, or until the potatoes are tender and the top is golden and bubbling. If you prefer a deeper color, you can broil the top for an additional 1–2 minutes — just keep a close eye on it to prevent burning. The cheese should be melted and slightly crisp at the edges, with small golden blisters forming across the surface.
