Prepare the Popcorn: Pop your popcorn using an air-popper or stovetop method. Make sure there are no unpopped kernels.
Make the Caramel Sauce: In a medium saucepan, melt the butter over medium heat. Add the brown sugar and corn syrup, stirring occasionally. Let the mixture come to a gentle boil and cook for 4-5 minutes.
Add Vanilla and Baking Soda: Remove the saucepan from the heat and stir in the vanilla extract and baking soda. The mixture will bubble, so be cautious.
Coat the Popcorn: Immediately pour the caramel sauce over the popcorn in a large mixing bowl. Use a spatula or wooden spoon to toss the popcorn until every kernel is coated.
Add the Nuts: Gently fold in the roasted peanuts and pecans (or your choice of nuts).
Cool and Serve: Spread the popcorn mixture onto a parchment-lined baking sheet and let it cool. Once it's cool enough to handle, break it into pieces and serve.