Tarte to tarte

Even the most proficient pastry chefs have seen plans for stunning cakes or confections go awry. But the mistakes haven't been all bad. Potato chips, popsicles, and chocolate chip cookies are all appetizing windfalls from things going wrong in the kitchen. And from across the pond: France's pièce de résistance, the (accidentally) upside-down apple tart known as Tarte Tatin - the apple of a wandering eye.

Unfortunately, those surprise aces can be hard to serve again. Most Francophiles who try to overcaramelize apples, butter, and sugar (just as Stéphanie Tatin did more than a century ago) tend to double fault: Their caramel is straw-colored, not dark amber, draped with pastry that's gummy and tough - nothing like the flaky puff familiar to French kitchens.

Thanks to Boston's recent bistro boom, though, we've been following beefy bavette steaks and shoestring spuds with slice after slice of the Parisian pastry, and we finally found a competitive duo at dueling South End bistros.

Both Aquitaine and Petit Robert featured apples deeply burnished by drench-worthy caramel. Petit Robert made classic strokes with thick apple wedges arranged concentrically atop a short (albeit denser) pastry. It almost rivaled Aquitaine's atypical take - a timbale-like mold of almost-burned apples seeping into a plush, buttery puff - until the latter's final shot: a moat of pleasantly bitter calvados caramel pooled around a dollop of crème fraîche.

Advantage, Aquitaine.

TRY IT TONIGHT Apple tarte tatin with calvados caramel and crème fraiche (left), $10

Aquitaine, 596 Tremont St., Boston. 617-424-8577. aquitaineboston.com

JUST TRY IT, ALREADY Warm apple tarte tatin with crème fraîche, $7.50

Petit Robert Bistro 480 Columbus Ave., Boston. 617-867-0600; 468 Commonwealth Ave., Boston. 617-375-0699. petitrobertbistro.com