Adjust a rack to the center of the oven. Preheat the oven to 350F. Grease the bottom and sides of a 9in by 9in casserole dish.

Set aside 1 ounce of Gruyere cheese for a cheesy crust.

Over medium-low heat, melt 1 tablespoon of butter and then add the garlic. Saute stirring for one minute before adding all of the heavy cream. Add the thyme and bring to a bare simmer and maintain for 10 minutes. Stir every minute or so to make sure it does not break.

While the cream is simmering, slice potatoes lengthwise with the mandoline set at ⅛ inch thickness. Don't forget to stir the cream occasionally. For your safety, use the cut resistant gloves out of precaution. Mandolines are not safe and should be handled with care.

Put a couple of tablespoons of the cream mixture on the bottom of the prepared baking dish. Overlapping slightly, put one layer of potato slices over the cream mixture. Sprinkle a pinch of salt and black pepper over the potatoes. Next spoon a light layer of the cream mixture of the potatoes. Make sure all of the potatoes are covered. Lastly, sprinkle a light layer of gruyere and parmesan cheese. Continue with the next layer of potatoes, salt and pepper, cream mixture, and cheese. Occasionally press down on the potatoes to compress the layers. Stop layering before you run out of potato slices or cream sauce.

Cover the baking dish with aluminum foil and put it in the oven. Bake until a knife or fork easily pierces the center of the baking dish. Check the doneness after one hour. If the test is successful, sprinkle 1 ounce of gruyere cheese on the top and put it back in the oven without the foil for 15 minutes. If the cheese is not browned to your liking, feel free to switch the oven to broil until the top is golden brown. Don’t walk away or answer the phone while your potatoes are under the broiler. Should only take a couple of minutes once the broiler is hot.

Remove from the oven and let rest for 5 to 30 minutes. It will be much easier to remove from the baking dish if you let it rest for 30 minutes. Enjoy!