Butter or oil an 8 inch square baking pan; set aside.
Put sugar, vinegar, syrup, and water in a heavy 4 quart saucepan (cast iron if you have it). Gently heat the mixture, stirring with a wooden spoon, until sugar has dissolved and syrup has melted. Bring to a boil, cover and boil for 3 minutes, then remove lid and boil until temperature reaches 285 degrees F (140 degrees C) on a candy thermometer. Remove from heat and stir in the baking soda, mixing well to allow bubbles to subside a little.
Pour hot mixture into prepared pan and leave until just beginning to set. Mark into squares with a lightly oiled knife. Leave to set completely. Cut or break into pieces.
Combine chocolate chips, shortening, and baking chocolate in a 2-quart glass bowl. Microwave on High for 2 minutes to melt. Stir with a wooden spoon. Dip candy pieces into chocolate, covering completely. Let cool on waxed paper.
Wrap individually in waxed paper, twisting the ends together, and store in an airtight container.