Scalloped Potatoes with Leeks

I recently came across this recipe when I was searching for a potato side dish to go with roasted chicken. I wanted to recreate the creamy, comforting, and homey taste of childhood Sunday dinners. Scalloped potatoes with leeks, tested by Martha Stewart sounded just right. The original recipe was first published in the March 2008 issue of Martha Stewart Living magazine. I picked up young fresh leeks and couple of large russet potatoes on my usual Sunday morning trip to the farmers market and couldn't wait to get started. Imagine thinly sliced leeks sauteed in butter until soft and fragrant, layered with hearty rounds of potatoes, creating an almost perfect culinary marriage. Add Gruyere cheese and cream to the mix and you'll have a combination of textures and flavors that can't be topped. Your gratin will be buttery, soft, and creamy on the inside and deliciously crusty and golden brown on top.
The original recipe states that this is a "do-ahead" dish and can be assembled the day before. I tried it several times, and noticed that if prepared in advance the potatoes inevitably change color. Even though I made sure the potatoes were completely submerged in liquid and covered with parchment paper to avoid oxidation, the top layers turned grey. Take my advice and don't start preparing the gratin the night before. It takes very little time to put this dish together and you won't end up with unpleasant surprises on the day of your party. Make sure to keep the peeled and sliced potatoes in a bowl of cold water until you are ready to assemble the casserole. Drain and dry the potatoes with paper towels before using.

Adapted from Martha Stewart Living Magazine


Ingredients
3 tablespoons unsalted butter, plus more for greasing your baking dish
3 leeks, white and light green parts only, trimmed, washed, and sliced thinly
6 medium russet potatoes, peeled and thinly sliced
1/2 teaspoon kosher salt
1/4 teaspoon freshly ground black pepper
1/8 teaspoon freshly grated nutmeg
3 cups Gruyere or Swiss cheese, shredded
1 cup heavy cream
1 cup low-sodium chicken stock


Preparation
Preheat oven to 350 degrees. Butter a 12 cup baking dish (12 x 9 inches).
Melt 3 tablespoons of butter in heavy skillet over medium heat. Add leeks and saute until softened and translucent, about 4-5 minutes. Remove from heat and set aside.
Mix together cream and chicken stock in a small bowl.
In a large bowl combine sliced potatoes with salt, pepper and nutmeg. Using your hands mix well until spices are evenly distributed.
Arrange 1/3 of the seasoned potato slices on the bottom of the baking dish. Cover with 1/2 of the leeks and 1/3 of the cheese. Repeat two times and finish with a layer of potatoes. Pour cream and stock mixture over the potatoes and sprinkle with remaining cheese. Cover with foil.
Bake for 30 minutes at 350 degrees. Uncover dish and increase oven temperature to 425 degrees. Continue  cooking until top is bubbly and golden brown and potatoes are tender, about 45 minutes. Let rest for about 20 minutes before serving.