Heat oven to 350 F.
Melt butter in a pan over medium heat.
Add leeks, season with ¼ teaspoon of salt and cook until softened, about 10 minutes.
Spread ½ of the potato slices on bottom of a greased 9x13 pan.
Top with ½ of the leeks and ½ of the shredded cheese.
Repeat with remaining potatoes, leeks and cheese.
In a small bowl, whisk together cream, milk, nutmeg and remaining ¼ teaspoon salt.
Pour over potatoes.
Cover baking dish with aluminum foil.
Bake in preheated oven for 40 minutes.
Remove foil, increase oven temperature to 425 F, and bake another 15 minutes, until bubbling and golden brown.
Serve topped with chives. Enjoy!