Preheat the oven to 300°F. Line a baking sheet with parchment paper or a silicone baking mat.
Pour the popcorn into a large bowl and remove any unpopped kernels.
Stir together the brown sugar, butter, and light corn syrup in a medium saucepan over medium heat. (Note: if you are using unsalted butter, you will want to add salt in step 4.) Stir until butter has melted and the mixture reaches a slow bubble. Stop stirring and allow the mixture to boil for 4 minutes.
Remove from the heat immediately and stir in butter extract and baking soda. The mixture will bubble up a bit. Stir in salt, if using. Stir in the pecan halves.
Pour the caramel-pecan mixture over the popcorn. Use a large rubber spatula to stir quickly but gently.
Spread the popcorn evenly on the baking sheet. Bake for 10-15 minutes, 10 for chewy and 15 for crunchy. Let cool in the pan about 10 minutes before serving. Chewy popcorn should be eaten the day of. Crunchy will last up to 1 week in an airtight container.