Just crossing the threshold of Matt Ross and Eric Finkelstein’s Carroll Gardens shop can lift a nostalgist’s spirits. Is that an entire shelf devoted to Quisp cereal over there? And who knew you could get (Cleveland) Stadium Mustard outside of Cleveland? Or Micucci Grocery puttanesca sauce without a trip to Portland, Maine? In short, you won’t find a better collection of oddball regional-American and certified-gourmet pantry items anywhere. Still, the reason you go is the sandwiches, quirky classics made to order, and gobbled down in the makeshift café next door. BEC variations like the Jersey-style pork roll on a Big Marty’s potato bun are a strong suit; the Italian combo is a TKO, even if it comes with an eccentric swipe of mayo; and the Reuben, a sweet, salty, fatty package of corned short-rib meat and zingy condiments wrapped up tight in Orwashers rye is the best in town.