Preheat oven to 375°. In a large bowl, beat butter and confectioners' sugar until blended. Beat in egg and vanilla. In another bowl, whisk flour, gelatin, baking soda and cream of tartar; gradually beat into creamed mixture., Divide dough in half. Shape each into a disk; wrap and refrigerate until firm enough to roll, about 30 minutes., On a lightly floured surface, roll 1 portion of dough to 1/8-in. thickness. Cut with a floured 2-3/4-in. flower-shaped cookie cutter. Press cutouts onto bottoms and up the sides of ungreased mini-muffin cups., Bake until edges are brown, 6-8 minutes. With the end of a wooden spoon handle, reshape the puffed cookie cups. Cool 5 minutes. Remove from pans to wire racks to cool completely. Repeat with the second portion of dough., In a small bowl, beat cream cheese until smooth. Gradually beat in confectioners' sugar. Pipe into cookie cups. Store in an airtight container in the refrigerator.