Place the popcorn in a very large, heat-safe bowl and set aside.

In a medium saucepan, combine butter, Karo syrup, and Red Hots. Bring to a boil over medium heat, stirring very frequently, and then reduce heat to medium-low and boil for 5 minutes. Stir in the cinnamon oil and then pour over the popcorn, stirring with wooden spoons to evenly coat the popcorn in the candy mixture.

Divide the popcorn evenly between the two baking sheets and spread in a single layer over each baking sheet. Bake for 30-35 minutes, stirring occasionally. Remove from the oven and allow to cool completely.

In a microwave-safe jar or measuring cup, add the chocolate chips and the shortening. Heat for 30 seconds at a time, stirring each time, until the chocolate is smooth and liquidy. Using a fork, drizzle the chocolate over the popcorn and allow to harden. Break into pieces and serve or divide into bags to deliver as gifts.