Spread popped popcorn on two large baking sheets lined with parchment paper. Quickly pick through it to remove any unpopped kernels. Preheat the oven to 250°F.

In a medium heavy-bottomed saucepan, melt the butter over medium heat. Once melted, add the brown sugar, corn syrup, and salt. The heavy bottom prevents scorching.

Bring the mixture to a gentle boil, stirring constantly with a wooden spoon or silicone spatula. Once it bubbles, set your timer for 5 minutes, stirring steadily. The mixture should darken and thicken.

After 5 minutes, remove from heat and stir in the baking soda and vanilla. The mixture will foam up – keep stirring until smooth, about 30 seconds.

Quickly pour the hot caramel over the popcorn, dividing it between both baking sheets. Sprinkle crushed apple chips and cinnamon over the caramel while it’s still hot.

Using two spatulas or wooden spoons, gently fold everything together until evenly coated. Don’t worry if it’s not perfect – it’ll get better in the oven.

Bake in the preheated oven for 1 hour, stirring every 15 minutes to ensure even coating and create clusters. It’s done when the caramel is glossy and dry to the touch.

Let it cool completely on the baking sheets. Once at room temperature, break up any large clusters into smaller pieces.