It's not really underground, but this tiny storefront might as well be, it's so damned hard to find. But once you do, owner Aileen Liptak will offer you everything from an iced chocolate cheesecake espresso to Turkish coffee to her own "Aileen Special." The comfy Williamsburg living room has free wi-fi with a purchase, and you can nibble on tater tots, buy the art off the wall, or read from any of the vintage paperbacks Aileen stocks. Every Thursday around 7, it's Board Game Night (with tater tots!). The gals seem to go for Scrabble while the guys crack open Risk. So the place has everything — except a credit-card machine. Sorry, cash only.