1-First, preheat the oven to 400 degrees and lightly grease a cast iron skillet to prevent sticking. Mix together the ¾ cup heavy cream and ¾ cup milk, then set it aside for later. Arrange an even layer of the sliced sweet potatoes in the skillet, ensuring they’re about ⅛ inch thick for uniform cooking.

2-Next, drizzle a few tablespoons of the cream mixture over the potatoes and season with kosher salt, freshly ground pepper, the 1 teaspoon fresh thyme, and a sprinkle of the cheeses ½ cup Parmesan and 1 ½ cups Gouda. Repeat this layering process with potatoes, cream mixture, seasoning, and cheeses to form 6 to 8 layers in total. Press down on the layers to submerge the potatoes in the cream, and add extra cheese on top if you want more crispiness.

3-Then, cover the skillet and bake for 30 minutes. After that, remove the cover and continue baking for another 30 to 45 minutes until the cream is fully absorbed, the potatoes are tender, and the top turns a beautiful golden brown. Finally, take it out of the oven and let it rest for 15 minutes to allow the flavors to settle before serving. Prep time is just 15 minutes, with a total cook time of about 1 hour, making it ideal for baking enthusiasts.