Beat cream cheese and butter in large bowl with mixer until well blended. Add flour; mix well. Refrigerate 1 hour or until chilled.
Heat oven to 350°F. Divide dough into 24 balls; place 1 in each of 24 miniature muffin pan cups. Press onto bottoms and up sides of cups to form shells. Beat egg in medium bowl. Add sugar and vanilla; mix well. Stir in nuts; spoon into pastry shells, filling each 3/4 full.
Bake 25 min. or until lightly browned. Let stand 5 min. in pans; remove to wire racks. Cool completely. Drizzle with melted chocolate. Let stand until set.