Step 1

Preheat the oven to 350°F/180°C and butter a casserole dish/baking dish (around 7x11inches; a 9x9-inch square may also work), using all the butter.

Step 2

Grate the cheese, mince the garlic, and mince the fresh thyme (just the leaves or the entire stem, if preferred).

Step 3

In a large bowl, combine the cheese, cream, thyme, garlic, and salt & pepper. Mix until well combined.

Step 4

Peel and thinly slice the potatoes to about 1/8-inch (3mm). I use a mandoline for this and transfer the cut slices directly into a bowl of water to stop them from browning.If you're using a knife, slice a thin section from one side of each potato so they rest flat against your cutting board.

Step 5

Once cut, drain them well, patting them dry with a clean kitchen towel. Transfer the potatoes to the bowl with the cream mixture and toss until evenly coated.

Step 6

Transfer the potatoes to the prepared baking dish. You can pour them straight in, only smoothing down the top OR you can arrange the potatoes into overlapping, tightly packed rows (refer to the pictures on the blog).By arranging the potatoes, the gratin has tons of edges at the top to become golden-brown and crisp.

Step 7

Cover the dish with a lid or some aluminum foil and bake for around 1 hour (I did 1 hr 10 minutes) or until the potatoes are fork-tender.

Step 8

Remove the foil/lid and continue to bake for 10-15 minutes, until golden on top. For a darker, crispier cheesy crust, broil the potato gratin for a minute or two at the end.

Step 9

Leave the au gratin potatoes to cool for 10-15 minutes before serving (to allow the creamy sauce/cheese some time to firm up), and enjoy!

Step 10

Store: Allow the potato au gratin to cool, and then store any leftovers in an airtight container in the fridge for 4-5 days.To Reheat: How you reheat the potatoes depends on the portion size. For small portions, a microwave will work (for around 2 minutes). For larger amounts, remove it from the fridge 30 minutes in advance, then cover the dish in foil and pop it back in the oven at 350ºF/180ºC until heated through (20-30 minutes).