Step 1

Preheat the oven to 400 degrees F.

Step 2

In a large bowl, combine the heavy cream and milk.

Step 3

Using a mandolin, slice the potatoes very thinly (if you don’t have a mandolin, you can use a knife, but it will be a lot more work and time). As you finish slicing each potato, place it into the cream milk mixture so the slices don’t brown.

Step 4

When the potatoes are all sliced, add the gruyere and parmigiano cheeses to the bowl, along with the garlic, the leaves from the thyme sprigs, salt, and a few cracks of black pepper. Toss well.

Step 5

Pour the potatoes and cream into an 8×11 baking dish, then cover the dish tightly with aluminum foil.

Step 6

Place the baking dish on a sheet pan, then bake for 1 hour.

Step 7

Remove the foil and bake for 30 minutes more, until the potatoes are tender, bubbling, and golden brown on top. Serve and enjoy!