1. Preheat oven to 350°F. In a medium bowl, beat butter, sugar, egg, chocolate, and vanilla with an electric mixer on medium speed until well blended.
2. Beat in flour and salt until dough is smooth, scraping down side of bowl frequently with a rubber spatula.
3. Spoon dough into a cookie press fitted with template of desired shape or a large pastry bag fitted with a large star or flower tip.
4. Press or pipe cookies 2 inches apart onto lightly greased cookie sheets. Bake 10 to 12 minutes, or until firm. Let cookies cool 2 minutes on sheets, then remove to wire racks and let cool completely. Store in a rightly covered container.