Creating this dish is a labor of love, much like the afternoons spent in Mama Lou’s kitchen, learning the secrets of her culinary magic. Follow these steps to make your own masterpiece:

1. Preheat your oven to 375°F (190°C).
2. In a large skillet, melt the butter over medium heat. Add the sliced onions and cook slowly, stirring occasionally, until they are caramelized, about 15-20 minutes.
3. While the onions are cooking, thinly slice the potatoes using a mandoline or a sharp knife.
4. In a mixing bowl, combine the heavy cream, thyme, salt, and pepper. Stir in half of the grated cheese.
5. Layer half of the sliced potatoes in a greased baking dish, followed by half of the caramelized onions. Pour half of the cream mixture over this layer.
6. Repeat the layering with the remaining potatoes, onions, and cream mixture. Top with the remaining cheese and breadcrumbs, if using.
7. Cover the dish with foil and bake for 40 minutes. Remove the foil and bake for an additional 15-20 minutes, or until the top is golden brown and the potatoes are tender.
8. Let the dish cool for a few minutes before serving. This allows the flavors to meld and makes slicing easier.

As you prepare this dish, remember that cooking is as much about instinct as it is about precision. Feel free to adjust the seasoning to your taste, just as Mama Lou taught me.