1. Beat butter at medium speed with an electric mixer until creamy. Gradually add granulated sugar, beating well. Add egg and vanilla, beating well. Combine flour and salt. Gradually add to butter mixture, beating until blended. Divide dough in half. Cover; chill 1 hour.
2. Roll each portion of dough to 1⁄4-inch thickness on a lightly floured surface. Cut with desired cookie cutters. (We used flower and starfish cutters.) Place on lightly greased baking sheets.
3. Bake at 350° for 8 to 10 minutes or until edges of cookies are lightly browned. Cool cookies 1 minute on baking sheets, and remove to wire racks to cool completely.
4. Dip cookies in Glaze and sprinkle, while wet, with sparkling sugar.