Grease an 8x8 inch baking dish. Set aside. In a medium bowl, beat cream cheese, sugar, and vanilla until smooth. In the top of a double boiler over lightly simmering water, heat white chocolate, stirring until melted and smooth. Fold melted white chocolate and pecans into cream cheese mixture. Spread into prepared baking dish. Chill for 1 hour, then cut into 1 inch squares.