Beat butter at medium speed with an electric mixer until creamy. Gradually add brown sugar, beating until blended. Add flour and salt, beating until blended. Stir in vanilla. Shape dough into 16 (1 1/4-inch) balls.
Place pretzel rods on ungreased baking sheets. Press a ball of dough onto cut end of each pretzel. Press dough firmly with a fork to resemble broom bristles.
Bake at 350° for 10 to 12 minutes. Let brooms cool on baking sheets on wire racks 2 minutes; remove to wire racks to cool completely.
Place brooms on wax paper. Spoon melted candy coating over pretzel and cookie where they join; let stand until firm. Decorate as desired with colored frosting.