Grease a large rimmed baking sheet or pan with cooking spray or line with a silicone baking mat.
Preheat oven to 225F.
Put popcorn on baking sheet, and place in the oven while you make the caramel.
10 cups popped plain popcorn
Add brown sugar, corn syrup, butter, and salt to a large, heavy saucepan.
1 ½ cups brown sugar, ¾ cup light corn syrup, ¾ cup salted butter, ½ teaspoon kosher salt
Bring the mixture to a boil, stirring constantly.
Let it boil 5 minutes without stirring.
Remove from heat.
Add baking soda and vanilla, and stir in to combine.
½ teaspoon baking soda, 1 teaspoon vanilla extract
Remove popcorn from oven, and pour caramel over warm popcorn, tossing to coat. The popcorn may not be completely coated, and that's ok.
Bake for 60 minutes, stirring every 15 minutes.
Remove from oven and let cool in a single layer on the baking sheet.
Break apart before drizzling with chocolate.
Once the popcorn has cooled and been broken apart, drizzle with chocolate.
2 ounces chocolate almond bark
Drizzle melted white chocolate over the top.
2 ounces white chocolate almond bark
Let the chocolate set up before serving.
Notes
Popcorn: It doesn't matter whether you use air popped popcorn or microwave popcorn as long as it's plain (unflavored) popcorn.
Butter: I use salted butter. If using unsalted butter, increase the salt to 3/4 teaspoon.
Brown sugar: Light brown sugar or dark brown sugar will work.
Salt: If you don't have kosher salt or sea salt, use half the amount of table salt.
Almond bark: I like to use white and chocolate almond bark because it's easy to find, especially around the holiday, and it melts and sets up nicely. You could substitute something similar, like candy melts, if you prefer.