This is a pretty simple side dish to make if you have a mandoline. If you don’t, then the slicing may get a bit tedious.
4 russet potatoes
1 1/4 cup heavy cream
3/4 cup milk
2-3 cloves garlic, peeled and lightly smashed
1 bay leaf
1 small sprig of rosemary
3 thyme sprigs
1 1/4 tsp salt
fresh ground white or black pepper and nutmeg to taste
1/2 cup grated Gruyère cheese
1/3 cup grated Parmesan
1. Put all of the ingredients except for the potatoes and the cheeses into a pot and bring to a simmer. Remove from heat, cover, and let steep for 30 minutes.
2. Preheat the oven to 325° F. Butter a 9″-square casserole, or you can go for a different shape around the same size. If you’re feeling French, you can first rub the pan all over with a cut clove of garlic.
3. Peel the potatoes, and slice them fairly thin, about 1/8″ (this is where the mandoline comes in). When you’re not working with them, keep the potatoes submerged in cold water so they don’t oxidize, but make sure you pat them dry before using them.
4. Arrange the potato slices in the pan, overlapping them, but keeping it to a single layer. Try to fit most of them in, but if your potatoes were on the large size you might have some left over. Strain the cream mixture, and pour it evenly over the potatoes. (If you taste the cream mixture, it will probably be delicious, but too salty. That’s okay, because the potatoes are as yet unseasoned, so it will all work out.)
5. Bake for 45 minutes, and then check it. The top should be browning a bit, and the potatoes should be cooked through (poke the center to make sure). In my experience, how long they take is highly dependent on how tightly packed your potatoes are, so give yourself some wiggle room, they may go longer.
6. Take them out of the oven, sprinkle with the cheese, and either put them back in for a few more minutes to get melty, or heat up the broiler and brown to desired crispiness.