in bowl of food processor fitted with metal blade. Add butter and cream cheese; process for several seconds, pulsing machine on and off, until mixture resembles rolled oats. (Alternately, by hand, place ingredients in mixing bowl and use pastry blender or 2 table knives to cut butter and cream cheese into flour.) Place mixture on lightly floured work surface; gather together a small amount to form into ball. To ensure even blending of fat and flour, smear ball of dough onto work surface with heel of hand. Repeat technique with remaining mixture. Gather dough into single mass and flatten into disk. Wrap in plastic wrap; refrigerate at least 30 minutes. When ready to bake, preheat oven to 350 degrees. Divide dough into 24 pieces. Place each piece into muffin mold, pressing dough firmly onto bottom and sides to form tart shells. To prepare filling: Mix together nuts, sugar, chocolate and eggs in small bowl. Divide mixture among prepared tart shells. Bake tarts until crusts are golden, 20 to 25 minutes. Remove from oven. Let cool 5 minutes, then unmold. Tarts can be served warm or cool. (Tarts can be made 1 day ahead. Keep in airtight container at room temperature.) When ready to serve, whip cream until soft peaks form. Gradually beat in brown sugar. Stir in rum. Whip until firm peaks form. Transfer to serving bowl. Arrange By Betty Rosbottom. ----