Steep the cream: Add the cream to a small pot over low heat. Add the garlic cloves, shallot, thyme sprigs, salt, and pepper. Barely bring to a simmer, then turn off the heat, cover, and let sit for 10 minutes.

Prepare the potatoes: Meanwhile, use a mandolin to slice the potatoes into thin slices, no thicker than ⅛ inch. If you don’t have a mandolin, you can use a knife, but take your time to get them into even, thin slices. Add the sliced potatoes to a large bowl of cold water to rinse off some starch.

Preheat the oven to 450°F. Liberally butter a large rimmed 11x14 half-sheet pan with butter. Get all the sides, corners, and the bottom.

Layer the ingredients: Remove the potato slices from the water and dry on a few clean kitchen towels or paper towels. Add half the slices to the sheet pan in a single layer, shingling the potatoes so they overlap slightly. Combine the gouda and Parmesan cheeses in a small bowl. Set aside about ⅓ of the cheese for sprinkling at the end. Sprinkle the layer of potatoes with half of the remaining cheese. Repeat, making another layer, with the potatoes and cheese going in the opposite direction. Remove the garlic, shallot, and thyme from the cream. Pour the infused cream over the potatoes, being careful to evenly distribute it all over.

Bake: Cover the pan with foil and bake for 30 minutes. At this point, the liquid should be bubbling and the potatoes should be tender around the edges of the pan but still pale on top. Remove the foil and add the remaining cheese, then return to the oven until the potatoes are very tender (easily pierced with a fork) and the top of the potatoes are lightly browned and bubbling, about 15 minutes. Let the potatoes cool for 5 to 10 minutes before slicing into servings. Garnish with chives and serve while warm. Leftover potatoes will keep in an airtight container in the fridge for up to 5 days. Love the recipe? Leave us stars and a comment below!