Preheat oven to 250° F.
Place popped corn into a large bowl; add toasted pecans on the top.
Heat the butter, brown sugar, corn syrup, and salt in a small saucepan over medium high heat. Bring to a boil, stirring until butter is melted. Reduce heat to medium low; cook, undisturbed and uncovered, for 5 minutes.
Remove saucepan from heat and stir in vanilla extract and baking soda.
Pour the caramel over the pecans and popcorn; stir to coat.
Spread the mixture onto an ungreased, large disposable aluminum roasting pan. (See Note 3)
Bake for one hour and 15 minutes, removing every 15 minutes to stir.
Spread the mixture onto parchment paper to cool. It may seem sticky at first, but will dry as it cools.
Once caramel corn is cooled, drizzle with melted dark chocolate.
Store in airtight container for up to a week.
Yield: 14 to 15 cups.