Combine chocolate and milk in a small Dutch oven; cook over low heat, stirring until chocolate melts. Add sugar and syrup; continue cooking, stirring constantly, until sugar dissolves and mixture comes to a boil. Cover and cook over medium heat 2 to 3 minutes to wash down sugar crystals from sides of pan. Uncover and cook, stirring occasionally, until mixture reaches thread stage (230°). Stir in butter and vanilla. Continue cooking until mixture reaches soft ball stage (236°).
Remove from heat, and cool to lukewarm (110°). Shape mixture into ropes, 3/8-inch in diameter; cut each rope into 1 1/2-inch pieces. Wrap each piece in plastic wrap or waxed paper.