-
1
Put the oven rack in center of the oven and preheat to 350 degrees F.
-
2
In a saucepan over low heat, add the cream and 3/4 cup of the walnuts.
-
3
Bring just to a simmer and then keep warm over lowest heat while building the potato layers.
-
4
In a large, lightly greased, 9 by 13-inch baking dish, arrange 1/3 of the potato slices covering the bottom of the dish, overlapping slightly.
-
5
Generously season with salt and pepper and sprinkle with a little sage, 1/3 of the Gruyere and a ladle of warmed walnut cream mixture.
-
6
Repeat 1 more time the exact same way.
-
7
Layer for a 3rd and last time with just the potatoes, making sure to arrange them in nice straight even rows.
-
8
Then cover the top of the potatoes with the remaining warmed walnut cream and top with the last 1/3 cup of the cheese.
-
9
Sprinkle with salt and pepper, to taste.
-
10
Cover with foil and bake for 30 minutes.
-
11
Reduce the oven temperature to 325 degrees and remove the foil.
-
12
Continue to bake until the top is just starting to become golden, about 20 minutes more.
-
13
Remove from the oven and do your best to let the gratin rest for 15 to 20 minutes before serving.
-
14
Eat and enjoy!
