Creating a delicious Creamy French Potato Casserole is easy if you follow these simple steps:

1. Preheat Oven: Preheat your oven to 375°F (190°C).
2. Prepare Potatoes: Peel the potatoes and slice them thinly using a mandoline or sharp knife.
3. Prepare Onion: In a skillet, heat olive oil over medium heat. Add the sliced onion and sauté until translucent, about 5 minutes.
4. Make Sauce: In a bowl, combine heavy cream, whole milk, minced garlic, salt, black pepper, nutmeg, and chopped thyme. Whisk until mixed well.
5. Layer Ingredients: In a greased baking dish, place a layer of sliced potatoes followed by a sprinkle of Parmesan, onions, and a pour of the cream mixture. Repeat until all ingredients are used, finishing with a layer of cheese.
6. Cover: Cover the dish with aluminum foil to prevent the top from browning too quickly.
7. Bake: Bake in the preheated oven for 40 minutes covered, then remove the foil and bake for another 20 minutes or until the top is golden and bubbly.
8. Let It Rest: Remove from the oven and let it rest for at least 10 minutes before serving. This allows the flavors to meld together beautifully.
9. Garnish: For an extra touch, sprinkle with fresh thyme leaves before serving.

By following these straightforward steps, you will have created a wonderful dish that’s sure to impress!