2 Tbsp unsalted butter plus additional for greasing the baking dishes
4 cups julienned leeks, white part only
2 lbs Yukon gold potatoes, peeled
2 lbs butternut squash, peeled and seeded
1 Tbsp chopped fresh thyme
Salt and pepper
1.5 cups heavy or light cream
1 tsp sweet paprika
1/4 tsp ground nutmeg
About 3 Tbsp grated local hard cheese for sprinkling
1. Preheat the oven to 350 F.
2. Lightly coat the interior of a 3-quart gratin (or baking) dish with butter. Set aside.
3. Heat the butter in a large frying pan over medium heat. Add the leeks and cook, stirring frequently, for about 7 minutes or until soft and translucent. Remove from the heat and set aside.
4. Using a Japanese vegetable slicer or a mandoline, cut the potatoes and squash into 1/2-inch thick slices. Transfer to a large mixing bowl and add the thyme. Season with salt and pepper and toss to coat evenly.
5. Place alternate layers of the potato/squash mixture and the leeks into the prepared gratin dish.
6. Combine the cream with the paprika and nutmeg. Season with salt and pepper and stir to blend. Pour the cream mixture over the vegetables in the gratin dish and, using a fork, gently move the vegetables so that the cream can settle into the dish. Sprinkle the grated cheese over the top.
7. Cover the entire dish with foil and transfer to the preheated oven. Bake for 45 minutes. Remove the foil and bake for an additional 5 minutes or until the top is golden brown and the vegetables are tender. You can test for tenderness by sticking the point of a small sharp knife into the vegetables; if it goes in easily the gratin is ready.
8. Remove from the oven and let rest for 5 minutes before cutting and serving.