Lady M Cake Boutique: Mille Crêpes Cake.   The Mille Crêpes Cake from this Upper East Side bakery is an absolute must-try this fall. Beneath the golden caramelized top are over 20 paper-thin handmade crepes, each sheet engulfed by a delicate layer of slightly-sweet pastry cream.   Lady M Cake Boutique, 41 East 78th Street (between Madison and Park avenues); 212-452-2222.