1. Preheat the oven to 375F. Grease 12″ cast-iron skillet with butter.

2. Combine the butter, heavy cream, sliced shallots, smashed garlic cloves, and herbs in a saucepan. Add a generous pinch of salt and a few cracks of black pepper. Bring to a simmer over medium heat. Reduce the heat all the way low and simmer for 15 minutes. Strain the cream into a large bowl.

3. Meanwhile, slice an end off of each potato. Thinly slice the potatoes on a mandolin, a little less than an 1/8” thick. The potato slices should be very thin and pliable. Add the potato slices to the cream. Gently toss to coat.

4. Layer half of the potatoes into the skillet in concentric circles, with one potato slice overlapping the next (season with salt and pepper after each layer). Distribute half of the gouda and gruyere across the potatoes.

5. Arrange the remaining potatoes over top in a few more even layers, seasoning again. Distribute the remaining cheeses over top. Pour all of the cream into the skillet.

6. Cover the dish with foil and bake for 1 hour. Uncover the dish and cook for 10-15 more minutes, or until golden. Let cool for a few minutes before serving. Top with more black pepper and any extra herbs.