BEAT cream cheese and butter with electric mixer on medium speed until well blended. Add flour; mix well. Cover and refrigerate at least 1 hour or until chilled.

PREHEAT oven to 375°F. Divide dough into 24 balls. Place 1 ball in each of 24 miniature muffin pan cups; press onto bottoms and up sides of cups to form shells. Beat egg lightly in small bowl. Add brown sugar and vanilla; mix well. Stir in pecans. Spoon evenly into pastry shells, filling each shell 3/4 full.

BAKE 25 to 30 min. or until lightly browned. Let stand 5 min.; remove tarts from pans. Cool completely on wire racks. Drizzle with melted chocolate. Let stand until set.