Cooking this dish is straightforward, much like those meals my mom used to whip up with just a few pantry staples. Let’s get started:

1. Preheat your oven to 375°F (190°C). Grease a 9×13-inch baking dish with butter or non-stick spray.
2. In a large skillet, heat the olive oil over medium heat. Add the onions and sauté until they are golden brown and caramelized, about 15 minutes. Stir often to prevent burning.
3. In a small saucepan, heat the beef broth and heavy cream until warm. Stir in the thyme, and season with salt and pepper.
4. Layer half of the potato slices in the prepared baking dish. Top with half of the caramelized onions and half of the cheese. Repeat with another layer of potatoes, onions, and cheese.
5. Pour the warm broth and cream mixture over the layers in the baking dish. Cover with foil and bake for 45 minutes.
6. Remove the foil and bake for an additional 15 minutes, or until the top is bubbly and golden brown.
7. Let the bake cool for a few minutes before serving. Garnish with parsley, if desired.