The violet-flavored merveilleux from Un Je Ne Sais Quoi. (Becky Krystal/The Washington Post)

A recurring series in which we'll spotlight a sweet treat for when you're in need of an afternoon sugar hit. Have a favorite you think we should check out? Share in the comments below.

What: Merveilleux

Where: Un Je Ne Sais Quoi, 1361 Connecticut Ave. NW. 202-721-0099.

Price: $5; $2.50 for the mini size

Sugar-meter score: 5, on a scale of 1 ("You call this dessert?!") to 10 ("I think I just burned a hole in my tooth enamel")

Merveilleux (pronounced MAIR-veh-yeuh) is the French word for "wonderful," and we can't think of a better word to describe this pastry that now has a bakery in Washington devoted to it.

Husband and wife team Aude and Francois Yann Buisine recently opened Un Je Ne Sais Quoi in the old Hello Cupcake space in Dupont Circle, and customers have been lining up to try their treats. Native to Belgium and northern France, merveilleux consist of whipped cream or ganache sandwiched between layers of meringue, all covered in another layer of whipped cream and chocolate flakes or other adornments, such as nuts, crumbled meringue or even cookie crumbs.

"It's very light," Aude Buisine said. "It's very airy." Un Je Ne Sais Quoi offers five flavors of their specialty: Dark chocolate, white chocolate, speculoos (the Belgian spice cookie), violet and coffee. (The bakery also sells a variety of other sweets, including meringues, tarts, eclairs and cream puffs.) Neither of the merveilleux -- about the size of a tennis ball -- we tried were overly sugary, with floral and spiced flavors balanced against the subtle sweetness in the violet and speculoos pastries, respectively.

Aude Buisine said the couple (she used to work at an employment agency, he owned a wine shop) gave up their life in Lille, France, to open the shop in Washington, which they had fallen in love with over the course of multiple vacations. Before opening Un Je Ne Sais Quoi, Francois spent many months learning the craft of pastries at a bakery in their home country.

"He likes good food, and he wanted to share that," his wife said.

Un Je Ne Sais Quoi also makes a speculoos-flavored merveilleux, right. (Becky Krystal/The Washington Post)

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