Gratin de Poireau et Patate Douce

1.Preheat your oven to 180°C (350°F).

2.In a large skillet, heat the olive oil over medium heat. Add the chopped onion and sauté for about 5 minutes until translucent.

3.Add the minced garlic and sliced leeks to the skillet, cooking for another 5 minutes until the leeks are softened.

4.In a large mixing bowl, combine the heavy cream, salt, black pepper, and nutmeg. Whisk until well mixed.

5.Layer half of the sweet potato slices in the bottom of a greased baking dish. Top with half of the leek and onion mixture.

6.Pour half of the cream mixture over the layers, then sprinkle with half of the Gruyère cheese.

7.Repeat the layers with the remaining sweet potatoes, leek and onion mixture, cream mixture, and finish with the remaining Gruyère and all of the Parmesan cheese on top.

8.Cover the baking dish with aluminum foil and bake in the preheated oven for 30 minutes.

9.After 30 minutes, remove the foil and bake for an additional 15 minutes, or until the top is golden brown and bubbly.

10.Remove from the oven and let it sit for 5-10 minutes before serving. Garnish with fresh thyme leaves.