When Gabe Stulman and Mehdi Brunet-Benkritly relaunched their quirky izakaya Chez Sardine as the breezy, neighborhood-friendly Bar Sardine, they and beverage director Brian Bartels excavated their childhoods and summers past for inspiration. The gastronomic regression therapy seems to have worked, as the narrow West Village canteen currently houses a remarkable ground meat sandwich. Originally created for the Montauk Burger Bash, Brunet-Benkritly’s “Fedora Burger” — named for, but never served at, the duo’s restaurant of the same name — crowns a chuck-and-brisket Pat LaFrieda patty with aggressive smoked cheddar and a jumble of shoestring potatoes. Raw red onions and pickles add welcome sharpness, but the burger’s barbecue mayonnaise is the most euphoric surprise — a smoky, sweet, unctuous special sauce deserving of the superlative, which enhances the beef rather than hiding it. Served on a soft potato roll, it’s a mighty $10 gut-punch. Fries sold separately.