4 lb leeks, white ad light green portions, cut into 1/4 inch rings
1 1/2 tbs. kosher salt
1 tsp minced fresh thyme
1/4 tsp freshly grated nutmeg
3/4 tsp freshly ground pepper
1 cup heavy cream
6 oz. Gruyere cheese, grated
3 oz. Parmigiano-Reggiano cheese, grated
3 lb. russet potatoes, peeled, cut into 1/4" slices
3 tbs minced chives
In a 12-inch nonstick fry plan over medium heat, melt 4 Tbs of butter. Add the leeks and salt, stirring to coat the leeks with the butter. Cover and cook, stirring occasionally, until the leeks are tender, about 20 minutes. Add the thyme, nutmeg, pepper and cream and simmer, uncovered, stirring occasionally, until thickened, about 15 minutes. Transfer to a bowl and let cool. Wipe out the pan and grease with the remaining 1 Tbs. cutter.
preheat oven to 400 F
In a bowl, combine the cheeeses. Layer one-third of the potatoes in the fry pan and spread one-third of the keep mixture on top. Sprinkle with one-third of the cheeses, and then 1 Tbs of the chives. Repeat the layering 2 more times, reserving 1 Tbs of the chives.
Cover the pan, transfer to the oven and bake for 45 minutes. Remove the lid and continue baking until the potatoes are tender and the crust is golden brown, about 30 minutes more. Sprinkle the remaining chives on top. Let stand for 15 minutes before serving. Serves 8 to 10.