The caramelized onions are the heart of this dish, contributing a delightful sweetness that complements the richness of the potatoes and cheese. Here’s how to get them just right:

Melt 2 tablespoons of butter in a skillet over medium-low heat.

Add the thinly sliced onions and stir to coat them in the butter.

Season with salt and pepper to taste.

Cook the onions slowly, stirring occasionally, until they begin to soften and brown.

Once the onions have taken on a golden hue, sprinkle with 1 teaspoon of sugar. The sugar will help the onions caramelize, turning them a deep amber color.

Continue to cook until the onions are completely caramelized—this should take about 15-20 minutes. Once done, set them aside to cool.

While the onions are caramelizing, you can start working on the creamy sauce that will envelop the potatoes.

In a large pot or Dutch oven, combine the heavy cream, half & half, grated garlic, fresh thyme sprigs, bay leaves, and a pinch of nutmeg.

Season with salt and pepper to taste.

Add the thinly sliced potatoes to the mixture.

Bring the mixture to a gentle simmer over low heat, stirring occasionally.

Let the potatoes simmer for about 15 minutes, or until they begin to soften. Be sure not to let them fully cook—they will finish cooking in the oven.

Remove the pot from the heat and let it rest for 10 minutes. Discard the thyme sprigs and bay leaves before assembling the dish.

While the potato mixture is resting, it’s time to get your baking dish ready.

Preheat the oven to 375°F (190°C).

Grease a 3-quart baking dish with the remaining 2 tablespoons of butter. This ensures that the potatoes won’t stick and that they’ll bake up golden and bubbly.

Now comes the fun part—layering the potatoes, caramelized onions, and Gruyère cheese to create a mouthwatering masterpiece.

Using a slotted spoon, layer half of the potatoes in the prepared baking dish.

Top the potatoes with half of the caramelized onions and half of the shredded Gruyère cheese.

Repeat the process with the remaining potatoes, onions, and cheese. As you layer, make sure the cheese is spread evenly over the potatoes for that perfect golden, bubbly top.

Pour the creamy mixture from the pot over the layers in the baking dish.

Now it’s time to bake!

Bake uncovered for 35-40 minutes, or until the cheese is golden and bubbly, and the potatoes are tender when pierced with a fork.

If the cheese is browning too quickly, you can cover the dish loosely with aluminum foil for the final 10 minutes of baking.

Once the dish is out of the oven, let it rest for about 15 minutes before serving. This allows the sauce to set and makes it easier to slice. If you like, you can garnish with fresh thyme for an added burst of flavor and color.