01 -
Heat the oven to 250°F. Line two rimmed baking sheets with parchment. Divide the popped popcorn between two very large heatproof bowls, removing any unpopped kernels.
02 -
In a medium saucepan, combine butter, brown sugar, corn syrup, and salt. Bring to a boil over medium heat, stirring often. Boil for 3 minutes, still stirring often.
03 -
Remove the pan from the heat. Stir in vanilla and baking soda until the caramel foams. Quickly divide it between two heatproof bowls, then tint one red and one green with gel food coloring.
04 -
Pour the red caramel over one bowl of popcorn and the green caramel over the other. Toss each bowl quickly with a silicone spatula until the popcorn is evenly coated.
05 -
Spread the popcorn on the prepared baking sheets. Bake for 45 minutes, stirring every 15 minutes, until the coating looks dry and glossy.
06 -
Cool completely on the pans. Break into clusters, mix the red and green popcorn together, and store airtight at room temperature.