March 31, 2008
I first made this tart—Gourmet‘s Onion Tart with Mustard and Fennel—a few weeks ago. And, trust me, I would have loved to post about it right away. But this tart has a super power that stood in the way. That’s right: this is a magically disappearing tart. When I first made it, as a little nibble for guests as they arrived at our bistro-themed Bon Voyage party for my friend Maggie, the tart vanished within mere minutes after I wielded my pizza wheel to slice it into squares.
I could’ve told you about what a joy the tart was to make, with its ethereal, spongy dough that rolled out like a dream and its loooong, slooooow caramelization of slim onion half moons. And I could’ve told you how heavenly the toasted fennel seeds smelled, how fun it was to slather the tart with Dijon mustard or how thrilled I was with the brilliant golden color the tart took on after a brief stint in the oven. But, beyond all this, it would have been a little difficult to describe a tart I didn’t even get to try (!). And, more importantly, how could I entice you with photos of scant crumbs on an empty platter?
(Click “more” for the rest of the story, more photos & the recipe.)
So, when I was home for Easter last weekend and we were pondering potential starters for our Easter Eve dinner, I knew it was just the chance (and the captive audience) I needed for a re-do. And this audience was comprised of family, which means I can boss them around. They might roll their eyes when I swat away the hands reaching in for a square before my photo shoot was complete, but they have to love me.
Now that I’ve got photos, I can show you how elegant this tart is. But, even better, I can describe it to you, because this time, there was a square to spare! Let’s start with the crust, which was cracker-thin and slightly salty; in short, a backdrop begging for a delicious adornment. Which brings me to the slick of Dijon coating the crust, which added a complex and unexpected dimension to the tart. And then we arrive at the onions. If you’ll excuse me for just one moment, I need to quickly swoon.
Okay, I’m back. Sorry about that—but this melty onion topping is entirely swoon-worthy. Apparently, when you allow thinly-sliced onions to bask over low heat in a fennel seed-spiked pool of olive oil for longer than an hour, onions that were once crunchy and abrasive will do quite an about-face. They will become supple and mild and just-this-side-of-sweet and (if I hadn’t made myself clear already) totally irresistible. In fact, I was shocked that such a truncated list of ingredients could yield an end product so transcendent. So, please, make this tart. And, when you do, take care to ensure that your fellow diners are not the types who will mind when you throw a sharp elbow as you dive in. Because when the dust settles, all that will remain will be crumbs. Or, if you’re very lucky, a stray onion.
Onion Tart with Mustard and Fennel
2 1/4 teaspoons active dry yeast (a 1/4-ounce package)
1/2 cup warm water (105-115°F)
1 1/2 to 1 3/4 cups all-purpose flour
1 large egg
1/3 cup plus 1 tablespoon extra-virgin olive oil, divided
2 1/2 teaspoons salt, divided
2 teaspoons fennel seeds
3 pound yellow onions, halved and thinly sliced
1 tablespoon Dijon mustard
1/2 cup grated Parmigiano-Reggiano
Stir together yeast and warm water in a small bowl and let stand until foamy, about 5 minutes. (If mixture doesn’t foam, start over with new yeast.)
Put 1 1/2 cups flour in a medium bowl, then make a well in center of flour and add yeast mixture to well. Stir together egg, 1 tablespoon oil, and 1 1/2 teaspoons salt with a fork. Add egg mixture to yeast mixture and mix with a wooden spoon or your fingertips, gradually incorporating flour, until a soft dough forms. Transfer dough to a floured surface and knead, working in additional flour (up to 1/4 cup) as necessary, until smooth and elastic, about 5 minutes. Transfer dough to an oiled bowl and turn to coat. Cover with plastic wrap and let rise in a draft-free place at warm room temperature until doubled, 1 to 1 1/2 hours.
While dough rises, heat remaining 1/3 cup oil in a 12-inch heavy skillet over medium-high heat until it shimmers, then sauté fennel seeds until a shade darker, about 30 seconds. Stir in onions, remaining teaspoon salt, and 1/2 teaspoon pepper, then reduce heat to medium-low and cover onions directly with a round of parchment paper. Cook, stirring occasionally, until onions are very tender and golden brown, 1 to 1 1/4 hours.
Preheat oven to 375°F with rack in middle.
Knead dough gently on a floured surface with floured hands to deflate. Pat out dough on a large heavy baking sheet (preferably blue steel) into a 15- by 12-inch rectangle, turning up or crimping edge, then brush mustard evenly over dough, leaving a 1/2-inch border around edge. Spread onions evenly over mustard, then sprinkle evenly with cheese.
Bake tart until crust is golden brown, 30 to 35 minutes. Cut into 2-inch squares or diamonds and serve warm or at room temperature.