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Mixed Onion Tart

April 8, 2012


Happy Easter! With the spring in full swing and our garden finally planted with the full rainbow of veggies and herbs, I’ve been feeling inspired.  But while my garden-grown veggies won’t be ready for at least another several weeks (lettuce, peas) or even months (tomatoes, cantaloupe, beans), the Thursday farmers’ market is overflowing with early spring goodies.  And the best of these might be the least mulled over: the lowly onion!

I first discovered onion tarts through a Nigella Lawson cookbook.  At the time, I thought it sounded a little…well…boring.  But I have come to realize that there is absolutely nothing boring about the world of onions; they come in a huge variety of colors and flavors, from sweet and zesty to bitter and earthy.  They can be red, white, yellow, brown, or green.  They can be as big as a baby’s head or as tiny as a thumbnail.  They come fresh, dried, even pickled!  And let’s not forget those fabulous onion cousins: leeks, shallots, and garlic.  And while most cured varieties (the common round red, brown, yellow, and white onions) are available year-round, the harvesting season for onions (and the only season when you can find them fresh at the Farmers’ Market) is spring.

Caramelizing onions takes them to a whole different level.  What was once so zingy it makes your eyes water and burn is now warm, sweet, soft and delicate.  It makes the perfect filling for this tart.  And topped with a range of other onion varieties, the flavor just goes on and on.  So grab a knife (and a box of tissues) and get a-slicing!

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Mixed Onion Tart

Ingredients

FOR THE CRUST
½ cup unbleached all-purpose flour, plus more for dusting
½ cup whole wheat flour
¼ teaspoon salt
½ cup (1 stick) unsalted cold butter, diced
2-3 Tbsp ice cold water

FOR THE TART
1 Tbsp unsalted butter
1 Tbsp olive oil
3-4 large white or yellow onions, thinly sliced
1 Tbsp white sugar
2-3 sprigs fresh thyme
2 medium leeks, white and light green parts only
4 spring onions, white and light green parts only
1 small red onion
Salt and pepper
Whole chives, for serving
Chevre or feta cheese, for serving

Method                 

  1. Stir together all-purpose flour, wheat flour, and salt in a medium sized bowl.  Add the butter and toss to coat each piece with flour.  To make by hand (as I always do) use the back of a fork to cut the butter into the flour.  If using a stand mixer, use a flat paddle attachment to beat the mixture on low speed until the mixture resembles coarse cornmeal.  Do not overmix, but make sure each piece of butter is no bigger than a pea.  Add the water one tablespoon at a time until the mixture pulls together but is not wet.  Shape the dough into a rough ball, being careful not to handle it too much, lest the warmth of your hands start to melt the butter.  Sprinkle the bowl with more flour and roll the dough ball in it to lightly coat.  Press ball into a disk, wrap with plastic wrap, and set aside in the refrigerator to chill.
  2. In a very large pan, heat the butter and oil over medium heat.  Add the sliced white or yellow onions and toss to coat. Watch the pan carefully and cook the onions, stirring occasionally, until they start to become soft and transparent.  Sprinkle with 1 Tbsp sugar and toss to coat.  Add the thyme sprigs and turn the heat down to medium-low.  Continue to cook the onions, stirring occasionally, until they are golden brown and completely soft, about 45 minutes.  If, as you are cooking, you start to see brown bits on the bottom, prevent them from burning by deglazing the pan: add a little water and scrape the bottom with a silicone spatula until they come up.  If the onions to start to burn or brown too quickly, reduce the heat and stir the onions.  Keep your eye on them!
  3. Meanwhile, split the leeks in half lengthwise and slice thinly.  Since leeks grow underground, they can accumulate a lot of dirt between the layers.  Wash them by adding the sliced leeks to a bowl of cold water and stirring it with your fingertips.  Let stand for a few minutes to allow the dirt to sink to the bottom of the bowl, then remove the leeks from the surface and set aside to drain.  Slice the green onions lengthwise into strips, and then thinly slice the red onion into rounds.  Toss the leeks, spring onions, and red onion together in a bowl and set aside.
  4. Once your onions are completely caramelized, remove them from the pan and set aside to cool.  Into the same pan, toss the mixed onions and cook just long enough to soften, about 5-10 minutes.  Remove from the heat and set aside to cool.
  5. Preheat oven to 350°F.  Remove the crust dough from the refrigerator.  On a floured surface, roll into a rough circle about 11 inches in diameter.  Carefully transfer to a 10-inch round tart pan, pressing into the sides.  Cut off any excess around the top.  Return to refrigerator to chill thoroughly, about 10 minutes.
  6. Remove crust from refrigerator.  Spread caramelized onions in an even layer over the bottom of the crust.  Top with the mixed onions and place in the oven.  Bake until the crust is golden and the onions are thoroughly cooked, about 45-50 minutes.  Remove from oven.  Serve warm and topped with chives and crumbled chevre or feta cheese.
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On buying and storing onions: Most common varieties of onion must be cured or dried just after harvesting.  This gives these onions their papery outer skin, which protects them from moisture that can cause mold and fungal growth.  But even fresh onions have a built-in mechanism to resist spoilage: high levels of sulfurous compounds repel bacteria and fungus (these are also the compounds that give onions their distinct zesty flavor and cause the reaction which makes eyes tear up).  For this reason, onions are easy to store long-term.  To buy cured onions, look for onions with an intact papery skin.  They should be heavy for their size fill out this skin with no soft or “empty” spots.  Remember, the harder to peel, the fresher the onion.  Cured onions can be stored for several weeks at room temperature in a dark place like the pantry.  Fresh onions, including spring onions, have no protective skin and must be stored in the refrigerator.  Choose fresh onions with bright green tops (yellowing is a sign of age).  They should feel dry, with no wet or slimy spots and no discoloration.  Dirt on the outside of onions is normal (they do grow underground, after all) and need not be avoided.  Just brush it off before purchasing to check the skin underneath for moisture or discoloration.  Use fresh onions within 1-2 weeks.

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