Heat oven to 250 Deg F (121 C). Set oven racks to the upper and middle third of the oven. Line two large baking sheets with parchment paper. Preferably lighter colored aluminum sheets.
Pop the popcorn, discard all un-popped kernels and place in a large bowl. Don’t add any butter or salt. Time for this will depend on your popcorn maker and or method. Takes me about 10 minutes to make two batches of popcorn
Pour the apple cider into a medium saucepan on the stove and bring to a boil. Boil until reduced to ⅔ cup (157 ml). You can check periodically by pouring into a measuring cup (use one that has at least one and a half cup measure in case it hasn’t reduced enough yet). This takes around 20 minutes. Once reduced transfer to a measuring cup or glass. Rinse the pan then add the butter. Lower heat to medium and melt the butter completely.
Next, add in the reduced syrup, brown sugar, maple syrup and salt. Stir until the sugar is dissolved and everything is mixed together well.
Stop stirring and raise the heat to bring to a boil. Boil for 4-5 minutes or until you reach 240 Deg F on a candy thermometer ( no more than 5 minutes if not using a thermometer.
Remove pan from heat and quickly whisk in the vanilla and baking soda. Be careful with this step since the caramel sauce will quickly grow in volume and bubble up.
Immediately pour the caramel sauce over the popcorn and stir with a spatula coating the popcorn as best you can.
Distribute the popcorn between the two prepared baking pans, scraping out any excess caramel from the pan and bowl
Place the pans in the oven and bake for a total of 45 minutes, stirring every 15 minutes.
After the first 15 minutes have passed, stir the popcorn to coat with the melted caramel sauce, swap the trays ( move one on lower to upper rack and vice versa). Bake another 15 minutes and stir and swap trays again. Then repeat for another 15 minutes.
Take the pans out of the oven and immediately sprinkle the caramel popcorn with the cashews and apple chips and stir so they will stick with whatever remaining melted caramel sauce there is.
Let cool then transfer to a large serving bowl or small bowls for individual portions.
This homemade caramel apple popcorn will keep well for weeks at room temperature kept in an airtight container.