Inspired by the Alsatian flammenküche, which is a tart with onions, cream, and bacon, this dish is an homage to cuisine from German-speaking Europe (Alsace, Austria, Belgium, and Germany in particular). Because we like to make things a little more interesting, we decided to add some leeks, crème fraîche, and a mix of herbs. Serve this tart alone, or paired with a Butter Lettuce and Pumpkin Seed Salad.
What to buy: Please take the time to make this dough from scratch, which will lend a flaky butteriness to the dish. Of course, if you are short on time, go ahead and use a store-bought crust. Just try to get the best you can find.
Crème fraîche is a naturally thickened fresh cream with a tangy flavor and a rich texture, and it does not curdle or separate when heated. If you can’t find it, sour cream is a decent substitute.
Game plan: Here are some tips on how to make the dough. It can be made well ahead of time and then rolled out and formed when you are ready to make the tart. Also, the onions and leeks could be sautéed up to a day ahead. Just don’t combine them with the herbs and the crème fraîche until you are ready to bake the tart, because you don’t want the flavors to become too intense.
1Melt 1 tablespoon of the butter in a large frying pan over medium heat. When it foams, add 1/3 of the onions and leeks. Season well with salt and freshly ground black pepper. Cook until onions and leeks are caramelized and golden brown, about 10 minutes. Season again with salt and pepper. Remove from the pan and reserve in a mixing bowl. Cook remaining onions and leeks in two more batches, using 1 tablespoon of the butter per batch.
2Combine herbs and crème fraîche with onion-leek mixture and check the seasoning. Add more salt and pepper as necessary, and let the mixture rest until it has cooled, about 5 minutes.
3Heat the oven to 425°F and arrange a rack in the middle. Lightly flour a work surface and roll the pie dough out into a round approximately 11 inches in diameter and 1/8 inch thick. Cut the dough into a 10-inch round (an overturned dinner plate and a paring knife work great). Lay the dough on a baking sheet and evenly spread the filling throughout, leaving a 1-inch border. Fold the perimeter of the dough (the outer 1 inch) over the filling and flute the edge by pinching it between your forefingers. (Check out our photo tutorial on How to Shape a Free-Form Piecrust for more information.)
4Make an egg wash by whisking the egg yolk with the cold water. Brush the outer edge of the tart with the wash. Place on the middle rack of the preheated oven and bake until the bottom of the crust is golden, about 20 to 25 minutes.
Beverage pairing: Serve with a light pilsner, such as Czechvar, or with a British stout, like Samuel Smith’s Imperial Stout. For wines, a cool, clean Pinot Blanc from, say, Alsace, Austria, or Oregon provides a creamy texture to complement this tart, along with just enough underlying acidity to cut through the richness. We recommend the 2005 Elk Cove Willamette Valley Pinot Blanc.