Ingredients:
5 tbsp. unsalted butter
4 lb. leeks, white and light green portions; rinsed well, cut into 1/4-inch rings
1 1/2 tsp. kosher salt
1 tsp. minced fresh thyme
1/4 tsp. freshly grated nutmeg
3/4 tsp. freshly ground pepper
1 cup heavy cream
6 ounces Gruyère cheese, grated
3 ounces Parmigiano-Reggiano cheese, grated
3 lb. russet potatoes, peeled, cut into 1/4-inch slices
3 tbsp. minced fresh chives
Directions:
1. Preheat oven to 400 F.
2. Heat 12-inch nonstick frying pan over medium heat, melt 4 tbsp. butter. Add leeks and salt, stirring to coat leeks with butter.
3. Cover and cook stirring occasionally until leeks are tender, about 20 minutes.
4. Add thyme, nutmeg, pepper and cream. Simmer uncovered, stirring occasionally until thickened; about 15 minutes.
5. Transfer to a bowl; let cool.
6. Wipe out pan, grease with 1 tbsp. butter.
7. In a bowl, combine cheeses. Layer one-third of the potatoes in frying pan. Spread one-third of the leek mixture on top. Sprinkle with one-third of the cheeses, and then top with 1 tbsp. chives.
8. Repeat layering 2 more times. Reserving 1 tbsp. chives.
9. Cover pan and transfer to oven. Bake for 45 minutes.
10. Remove lid and continue baking until potatoes are tender and crust is golden brown, about 30 minutes more.
11. Remove from oven and sprinkle with remaining chives. Let stand for 15 minutes before serving.