Almond shortbread pastry

Something’s astir at a few of the best bakery addresses in Paris, and you can tell by the shape of their tarts.

They are decidedly, perfectly, unexpectedly square.

“We were a bit frustrated with round,” says Jean-Charles Carrarini, who along with his wife, Rose, owns Rose Bakery in the 9th arrondissement. “Everyone had round -- and they weren’t deep enough. Rose wanted to change them visually.”

The two designed their own tart molds and had them custom-made by “a bit of an artist” in Paris. So now the white marble counters are stacked with individual savory tarts that people line up for, and they are very square -- the tarts, that is.

Master baker Eric Kayser of La Maison Kayser, also the owner of L.A.’s two Breadbar stores, has been making square tarts too. They’re featured in his just-translated-into-English book, “Eric Kayser’s Sweet and Savory Tarts” (Flammarion). Almost all of them are pleasantly square: damson plum dusted with sugar and cinnamon, tangerine and almond cream, custardy cherry clafoutis tart, onion and sausage, artichoke and Parmesan, chanterelles and duck.

Kayser says that at his 11 bakeries across Paris, the square tarts are especially popular (“I like the different shape ... and they are easy to eat.”). They’re so appealing because of their sharp corners and clean, straight sides.

These square tarts -- the Carrarinis’ and Kayser’s -- make a bold statement because they also signal a growing appreciation for thoughtfully crafted but wonderfully rustic pastries in a city where fussily fantastic patisseries still rule.

Among all the high-end, uber-chic treats in Paris, these pastries are celebrated for being simple but beautiful. Their fillings are straightforward, their crusts maybe slightly rough-edged (but just so).

They’re not like patissier Pierre Herme’s tarts, round and intricately constructed with layers of ganache, dacquoise, Chantilly cream, gelees, croquante, tempered chocolate or pastry cream.

Or like those of pastry chef Sadaharu Aoki, whose eponymous shops sell tarts dusted with green tea powder or garnished with shards of white chocolate -- that also happen to be round. (An occasional tart at fancy food shop Fauchon might be square, such as its carre citron, a square lemon number topped with elaborately decorated white chocolate tiles. And pastry shop Gerard Mulot has a square apricot tart, the fruit standing up in rows like soldiers.)

Nor are they textbook tarts, from instructional tomes for pastry chefs, such as the somewhat whimsically titled “Apprenez l’Art de la Viennoiserie et Festival de Tartes” (“Learn the Art of Viennoiserie and Festival of Tarts”), which includes not only photographs of elaborate tarts but also precise technical drawings for “the exact structure of the product.”

The diagrams point to each layer: Breton shortbread, liquid chocolate (applied with a spray gun), jellied berry coulis, pistachio pain de Genes, light pistachio cream, white chocolate decorations and fresh fruit decorations, for example. And none of the tarts at this festival are square.

“When I opened my first bakery, I wanted a bakery that broke with the traditional French bakeries,” says Kayser, a fifth-generation baker known for helping to reinvigorate bread baking in France, selling only breads with levain (made with natural yeast). “It was the same for the tarts. Traditional French bakeries offered too-sweetened tarts with the same fruits.”

Kayser’s tarts are just sweet enough -- many piled high with fruit, some not even baked into the tart -- a mountain of blueberries on top, a pile of strawberries, rows of raspberries, a swirl of tangerine segments.

A favorite is the apricot pistachio tart, layered with stunning apricot halves tucked into a delicious pistachio filling that creates what looks like rolling hills in between the fruit.

Among Paris’ big-name bakeries, wildly popular Rose Bakery is an anomaly, a bit of a square peg in a round hole, if you will. Located in a former chartil (a place where the old fruit barrows for the markets were kept), the bakery serves up date and oat slices, carrot cake and jam sandwich vegan cookies along with its square tarts.

It’s “fresh and simple cooking,” writes Rose Carrarini in her recently published first cookbook, “Breakfast, Lunch, Tea: The Many Little Meals of Rose Bakery” (Phaidon). “I am not very fond of sweet things and sugar, and yet I became a pastry chef.”

There’s another Rose Bakery at the Dover Street Market, the London shop conceived by fashion designer Rei Kawakubo. And more are planned for Paris. “We are looking desperately to open a new concept,” Jean-Charles Carrarini says. “We just haven’t found the right space yet.”

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Eat your veggies

IT’S a good thing they have the right pans though, because they’re not easy to find. “We wanted people to eat vegetables,” says Jean-Charles, and the molds they found were all “a bit too shallow. You could only fill them with the cream and no vegetables.”

Their specially made tart molds are straight-sided (as opposed to fluted) and deep, so the couple can fill their tarts with plenty of vegetables and handfuls of herbs -- mushrooms with long strands of chives or a tomato and ricotta tart chock full of thyme, its pastry crust (made with Lescure butter from Normandy) lined with cheddar from Neal’s Yard Dairy in London.

“We keeping making more tarts and keep having more tart molds made,” Jean-Charles says.

It’s difficult to track down a straight-sided square tart pan, but square tart “rings” are available online at www.meilleurduchef.com (in French and English). They’re bottomless, so your parchment-lined baking sheet becomes the “bottom.”

Kayser says he uses molds from a “special provider” but recommends steel pans from French restaurant supplier Mora, www.mora.fr (in French only), though they’re not bottomless, nor do they have removable bottoms. That’s fine if you don’t mind being unable to unmold the tart -- you just cut it and lift out the pieces.

Or you can use a widely available fluted, square tart pan.

The shape of one’s tart is almost a philosophical issue. It’s certainly an aesthetic one. Circle or square, circle or square?

Ask the baker who named one of his tarts “Muskmelon in a Geometric State of Mind.” Maury Rubin, owner of the City Bakery in Los Angeles and New York and author of “Book of Tarts: Form, Function and Flavor at the City Bakery,” is squarely in the round camp. Blame it on his affection for the round flan ring.

“I love it purely as an object,” he writes in his book. “As industrial equipment goes, it is beautiful and elegant. Working with the flan rings will expand your baking experience.”

But would he ever make a square tart?

“God, I love that question,” he says. “I can’t begin to tell you how much I love that question. I’m not even going to answer it because it might take the focus off of how much I love the question.”