Not all European designers in New York this week came for the Costume Institute fete. Alexis Mabille, one of the bright young lights of Paris fashion, is in town to celebrate a friend's birthday. His Gotham sojourn provided a break from working on the collection he will show during the July haute couture season, the follow-up to his breakthrough effort in January in which he turned his fancy for fanciful bowties into a fabulous lineup of young, alluring clothes. While Mabille hopes to retain the chic factor next time out, he won't show at Angelina's tearoom again, and not only because the venue is too small to accommodate his growing guest list. It seems that Mabille has transferred his allegiance to another famed Parisian sweets emporium, Laduree, for which he has designed a bowtie cake, to hit the menu in June in several delectable flavors including citrus, strawberry and pistachio. "It's interesting to do something completely new," he said. Speaking of which, while his New York exploits typically center on downtown, this trip has taken Mabille off the beaten path of hip. On Wednesday a friend took him to the Frederick Law Olmstead Awards luncheon in Central Park's Conservatory Garden, named for the park's great landscape architect. There, he marveled at "all these ladies dressed in pastels." And one evening he found himself at Swifty's. "It wasn't young," he said, gallantly ignoring the occasionally indiscreet nips and tucks one might notice in such a venue. Rather, Mabille gauged the crowd by its accoutrements: "So many JAR earrings! So many Cartier necklaces!"