Combine flour, sugar, cocoa and salt, set aside.
Combine butter and vanilla and beat until fluffy. Gradually beat in flour mixture until well combined.
Cover and chill dough at least 30 minutes.
Preheat oven to 350 degrees. Form dough into 1 1/2 in. balls. Roll balls gently to form 5 - 6 in. logs about 1/2 in. thick. Shape into worms 2 in. apart on ungreased cookie sheets.
Bake 12 min. or until set.
Make eye dots and mouth stipes on worms with frosting.