Active Time

　　25 min

　　Total Time

　　1½ hr

　　Cutting leeks into large pieces (they almost dissolve when thinly sliced) gives them a presence equal to disks of potato, while cooking the vegetables separately—the leeks are braised in butter, the spuds are simmered in milk and cream—preserves their distinct flavors. The glorious results will supply the homiest meatloaf supper with pizzazz.  

　　  

　　This recipe was developed for Gourmet magazine's December 2009 issue. Unfortunately, Gourmet was shuttered before that issue was published. So in 2018, we dug up the entire Christmas menu and posted it here.

　　

Ingredients

8 servings

　　9 medium leeks (about 3 lb; white and pale green parts only)

　　3 Tbsp unsalted butter

　　2 lb russet (baking) potatoes

　　1½ cups heavy cream

　　1 cup whole milk

　　2 tsp thyme leaves

　　

Special Equipment

An adjustable-blade slicer

　　

Step 1

Preheat oven to 400°F with rack in middle. Generously butter a 3-qt shallow baking dish. Cut a round of parchment paper to fit just inside a 12-inch heavy skillet, then set parchment aside.

　　

Step 2

Halve leeks lengthwise, then cut crosswise into 1½-inch pieces (you should have about 8 cups). Wash leeks.

　　

Step 3

Cook leeks in butter with ½ tsp salt and ¼ tsp pepper, covered with parchment round, in skillet over medium heat, stirring occasionally, until tender, 10 to 12 minutes.

　　

Step 4

Meanwhile, peel potatoes and slice crosswise 1/16-inch thick with slicer. Transfer to a large heavy pot with cream, milk, thyme, 1 tsp salt, and ½ tsp pepper and bring to a boil over medium heat, stirring occasionally (liquid will thicken). Stir in leeks, then transfer to baking dish.

　　

Step 5

Bake, uncovered, until potatoes are tender, 45 minutes to 1 hour. Let stand 10 minutes before serving.

　　

Do Ahead

Step 6

Gratin can be baked 2 days ahead and chilled. Let stand at room temperature 30 minutes, then reheat, covered, in a 350°F oven until hot, about 30 minutes.