A delightful twist on a classic gratin, combining creamy potatoes, sweet butternut squash, and savory leeks.
Preheat your oven to 375°F (190°C).
Preheating ensures even cooking and a perfect golden crust.
Generously butter a 3-quart baking dish.
Use a paper towel to evenly spread the butter and avoid sticking.
In a skillet over medium heat, cook the leeks in 2 tablespoons of butter until soft and fragrant.
Stir occasionally to prevent the leeks from browning too much.
In a saucepan, melt the remaining butter over medium heat, then whisk in the flour to create a roux.
Cook the roux until it smells slightly nutty for better flavor.
Gradually add the milk to the roux, whisking constantly until the sauce thickens.
Warm the milk beforehand to prevent lumps in the sauce.
Peel and thinly slice the potatoes and butternut squash.
Use a mandoline slicer for even slices and quicker preparation.
Layer the baking dish with a third of the sauce, followed by a third of the potato and squash slices, a third of the leeks, and a third of the cheese. Repeat for two more layers.
Press down gently on each layer to compact the ingredients for even cooking.
Cover the dish with foil and bake for 30 minutes. Then, remove the foil and bake for an additional 20 minutes until golden and bubbly.
Let the gratin rest for 5 minutes before serving to set the layers.
Serve the gratin warm, garnished with fresh herbs if desired.
Pair with a crisp salad or roasted vegetables for a complete meal.
