This is where the city’s preeminent Spanish-food couple, Alex Raij and Eder Montero, came up with the “uni panini,” easily one of the greatest sandwiches of the past decade. Its genius lies not in the concept of plopping blobs of sea urchin onto a ficelle (your average Frenchman has been doing that forever) but in Raij-Montero’s having found a soul mate for the uni in the form of a butter they flavor with Korean mustard oil. This type of flourish is standard practice at EQP. Eggs are scrambled with sea anemone. Manchego is marinated in za’atar. Mackerel comes with a side salad … of kombu. Is it traditional? Modern? An old family recipe? Raij and Montero also run the Basque joint Txikito across the street and La Vara in Brooklyn, which explores Spain’s Moorish and Jewish culinary legacies, but El Quinto Pino, which expanded from a standing-room bar into a bona fide restaurant, is the most eclectic and experimental of the bunch, not to mention the least expensive.