Somehow, when your doctor sends you to a spa, you feel justified.So you can imagine our thrill when — after running to the dermatologist after a heinous breakout (too much candy?) — we were ushered upstairs to the sleekest spa we’ve spied in awhile.It was insane. A slate waterfall. Bamboo floors and walls of Japanese sea grass. Wasabi peas and crispy edamame in the waiting room. Butter-soft robes. We had the facial. Creams and masks that alternated in scent from eucalyptus to cake-batter. A scalp rub, a foot rub. Then the fun really began. We were whisked away, tag-teamed by two Ayurvedic therapists who rubbed us down, drizzled warm oils all over our back, flipped us over, rubbed us down again, swirled more warm oil up and down our belly, wrapped us in banana leaves, and then plinked us in the shower.The concept of medical spas is not new. But the Mezzanine Spa, the latest creation from the offices of Dr. Laurie Polis, is a pretty slamming specimen. The best part: It’s around the corner from Balthazar. So you can pop out the door, sit your purified self down, and undo all the good things you’ve just done with a stiff drink and a big plate of greasy fries.