But Jimenez has built an impressive resume since arriving, rising from dishwasher and prep cook to become an integral part of the kitchen at Vetri, where he finished an eight-year tenure as sous chef.
And Cook, who owns West Philly's Marigold Kitchen (where he was also the opening chef), knows a thing or two about the Vetri culinary farm, having already plucked one former sous, Michael Solomonov, to succeed him in the kitchen at Marigold.
Cook and Jimenez would become equal partners at Xochitl (so-cheat), which means flower in the Aztec language of Nahuatl. But this ambitious restaurant's intriguing approach to Nuevo Mexican cooking is clearly built on Jimenez's vision - an intimate understanding of authentic flavors updated with a contemporary touch, high-grade ingredients, and a lightness that defies the leaden and over-spiced cliches of Mexican cooking.
At their best, Jimenez's creations are vivid and stunningly original. That seviche, for example, takes one brilliant pairing - scallop and watermelon - and hones it to its most elegant presentation, with a nearly translucent layer of sliced raw scallops laid atop a paper-thin round of pink fruit. The contrast of textures and flavors - the juicy crunch and sunny sweetness of watermelon against the buttery slip and gentle marine tang of the scallop - was subtle but so startlingly good I can still taste it.
Jimenez has a noticeably light touch, but can also indulge in some of the lusty, rustic flavors of his native Puebla. Among the best is his chile en nogada, a plump poblano pepper stuffed with ground beef, toasted almonds and dried fruit that comes glazed in a pool of walnut cream jeweled with rubylike pomegranate seeds. The richness of the dish, with an exotic whiff of cinnamon to the meat, gave way to a swelling tingle of chile heat.
His cazuela of tender squid and mushrooms roasted in a deep brown paste of fried garlic and guajillo chiles is so intensely earthy it could be the Mexican definition of savory.
Xochitl's barbacoa de borrego is another instant classic. A chunk of lamb leg and rib is marinated in avocado leaves and agave nectar before being braised to a soulful tenderness for nearly 10 hours. It has a peasant oomph that tastes like a Mexicanized rendition of Vetri's roast goat.
Whether Jimenez's cooking can someday rise to the level of his mentor's is an open question, as this early menu still has lots of fine-tuning to do.
But Xochitl already has in the works the promising ingredients of a complete restaurant experience. The space, set into a storefront on Head House Square that used to be Filo's (and the jazz club Cafe Borgia many years before that), is intimate and warm, with a cozy dining room and upstairs bar accented by Mexican tilework, Latin wood furniture, and wrought-iron details. There is a sultry, pillow-strewn downstairs lounge that seems ready-made for a tequila-scented tryst.
And Xochitl has plenty of excellent tequilas to choose from - including top labels like El Tesoro, Corralejo and Casa Noble - that can be ordered by the shot, in flights of three, or jarrito-style: served in carved-out cucumber cups with a cleansing side of spicy, gazpacholike sangrita.
Xochitl's attentive and friendly service staff was impressively well-versed on the tequilas and unusual cocktails (go for the Mexicanized mojito with thyme called Sr. Barriga), as well as Jimenez's menu, which usually demands plenty of explaining for those with experience limited to the old Tex-Mex burrito special.
Much of the fare here, in fact, is more classic than expected after tasting Jimenez's inventive creations. The queso fundido is a just a crock of melted chihuaha cheese (although there's nothing wrong with that). His sopa Azteca simply distills tortilla soup to its earthy, guajillo essence.
But the three other seafood seviches are redundantly sauced in a similar tomato-based salsa. They're fresh, but a bit boring once you've had the scallop-watermelon fantasy.
I'll never get tired of fresh guacamole made tableside, though Xochitl's rendition is still a squeeze of lime shy of the zippiest one still being made at El Vez.
Jimenez does get creative elsewhere, but a number of dishes still need some extra tweaks to sing. The guajillo soup with rabbit and snails has the right flavors (and who'd have thought, quipped one guest, that those two would ever end up in the same pot?) But it would work better in a more intensely reduced sauce than a brothy stew. I'd love the gordita pockets stuffed with huitlacoche - if only the masa dough were more delicate so as not to overwhelm the delicate dark bubbles of corn "mushroom" inside.
Xochitl features some excellent ingredients, like the gargantuan head-on Mayan shrimp baked beneath a mountainous crust of tequila-moistened salt. Once those shrimps were removed from their shells in the kitchen and plated, though, they were surprisingly bland (a sauce might help) and slightly undercooked. A big rib eye in pasilla chile gravy was not as fine a piece of meat as I had hoped for $28.
For the most part, however, Xochitl's entree prices, hovering in the low $20s, are reasonable for the quality of cooking. Jimenez even delivers a dessert list with real distinction.
His churros with chocolate and dulce de leche are among the best in town - those sugar-crisped batons of fried dough still puddinglike inside. Delicate, tuilelike tubes of tacos dulces come wrapped around a tangy froth of tequila mousse. My favorite, though, was the surprising tartaleta, an elegant round crust topped with pastry cream, tangy mango, buttery ribbons of avocado and the sparkling crunch of kiwi.
With more startling and vibrant flavors like that, the "Dionicio business" should be booming soon.
Contact restaurant critic Craig LaBan at 215-854-2682 or firstname.lastname@example.org.
Read his recent work at http://go.philly.com/craiglaban.