Potato and parmesan gratin

Okay so I don't often make potato recipes that involve lots of cream and cheese. But for this week's Summer Fest, featuring potatoes, I decided to forget about nutrition and make something decadent. I went with a potato gratin from Gourmet Today that they describe as "the ideal marriage of potatoes and cheese" - if Gourmet says it, I believe it! I was lazy with this recipe - I didn't peel the potatoes, and coarsely grated the cheese to avoid giving my arm a workout by finely grating. Maybe that made it a bit less pretty, but it still tasted good!

Potato and parmesan gratin
Adapted from Gourmet Today
Serves 8

4 pounds medium boiling potatoes
1 1/2 tsp fine sea salt or table salt
1 cup heavy cream
1 cup whole milk (I used 1%)
3 tbs softened unsalted butter
7 ounces finely grated Parmigiano-Reggiano cheese (2 1/3 cups)

Put a rack in the middle of the oven and preheat to 350 deg F. Peel potatoes (or not, if you don't mind the peels) and cut into 1/8-inch thick slices - a mandoline is very helpful here. Spread potato slices out on a kitchen towel and sprinkle with salt.

Mix together cream and milk. Dot the bottom of a 9 x 13 inch pan with 1 1/2 tbs butter. Pour in 1/3 cup of the cream mixture. Layer one fifth of the potatoes in the dish (don't rinse or dry them), drizzle with 1/3 cup cream mixture, and top with one quarter of the cheese. Repeat 3 more times (this will use up all the cheese). Top with the last one fifth of the potatoes, and drizzle with the remaining cream mixture. Dot the top layer with the remaining 1 1/2 tbs butter.

Bake gratin uncovered in the preheated oven until potatoes are very tender and the top is browned, about 2 hours. Let sit at room temperature for about 10 minutes before serving.