Kvetchin’ in the kitchen

HERE’S some friendly advice for Ulrich A. Sterling, the executive chef of new, “pan-Latin” Agua Dulce: Rather than clobbering a critic who claimed to find a nonexistent waterfall in your joint, kick some butt in your kitchen.

I’ve been to Agua Dulce four times. The only time it really clicked was when the house knew to expect me. That night, it proved there’s real talent at the stove. But it doesn’t count if it only shows up for a snarky, cranky reviewer.

Agua Dulce personifies the new Ninth Avenue, where elaborately designed eateries have begun popping up amid the ethnic mom-and-pops. The look is an eye-pleasing splash of today’s South Beach, pre-Castro Havana and what the place calls “the Golden Age of Latin America,” whenever that was.

Aquamarine tile, black-and-white-striped wood, yellow-and-blue brick and wrought-iron filigree scream that you’re having fun. So do turquoise booths big enough for an entire pueblo and a noise level high enough to cause balance problems.

There’s a three-story “liquor tower” behind the bar; partake too heavily and you proceed at your own risk up the steps to a cozy rear mezzanine or down to a dimly lit lower level.

With a well-priced menu (dinner starters $10-$14, mains $18-$23) that mines and adapts favorites from the Spanish-speaking Americas and Brazil, Agua Dulce mightn’t have raised a ripple. Nor would its shtick of selling bubble-infused, charcoal-filtered tap water for $3 with proceeds going to the “Latin American Clean Water Initiative of the Resource Foundation” seem so annoying.

But then Sterling, who once worked under Nuevo Latino god Doug Rodriguez, went gunning for an anonymous Time Out New York reviewer in a tirade he thoughtfully sent to GrubStreet.com.

The critic had cited a phantom wall of “cascading water,” mistook skirt steak for hanger steak and called Sterling’s food “inauthentic.” The chef snorted that he wasn’t trying to be authentic. Or something like that: It’s hard to tell what he meant by, “Our intent . . . is to embrace, not focus on” Central and South American styles.

Well, dude, embrace this: Your lunchtime frisee salad with Manchego cheese contained no Manchego. Asked about it, the waiter first claimed it wasn’t supposed to, then sheepishly brought cheese on the side. Salmon ceviche was a fussy, slimy, salty blur. Chicken slices atop an ottoman-like round of saffron Valencia rice were the dry, flavorless salad-bar article.

What a different story on the night when Sterling and a platoon of managers hovered over our every morsel. Ginger-kissed butternut squash soup was light on the tongue and grilled salmon as juicy as its skin was crisp.

This time, the salmon ceviche had distinct jalapeño and citrus notes. Coconut-milk broth in Brazilian seafood stew was fresh, unlike the gummy mess I had this summer. Tea-braised beef short ribs were tender enough to eat with a spoon. Such fine, Modern-American dishes with varying degrees of Latinization were worthy of Sterling’s bluster.

But a restaurant is supposed to be good all of the time, not just when it’s at battle stations. On a night when the B-team was on deck, entrees took 55 minutes to arrive. Off-balance butternut squash soup was less soup than purée.

The seafood stew had no shrimp, only a monotonous heap of mussels and clams; the rice cake on top was burnt. “Bacalao con bacalao” was actually fresh, not salted and dried, cod in a crust that’s supposed to include salted cod with yuca, onions and herbs, but tasted like generic schnitzel breading.

Desserts including molten chocolate cake with a chocolate chili splash are so yummy, it would be a shame to skip them, as we did once when the din was just too much. Agua Dulce’s noise problem isn’t its loud customers, though — but its own big mouth.

scuozzo@nypost.com