Pour 1/4 cup of dry popcorn kernels into popcorn machine as picture below.
Connect to power, put the cover and lid on. Let the machine run and couple minutes later popcorn will come out.
Using a big bowl to hold the air popped popcorn
Put parchment paper on a cookie sheet then lay popped popcorn on it and preheat oven for 200 F
Add butter into a non-stick pan or pot and turn on fire to medium low. Let the butter melt, add brown sugar, syrup and salt continue to stir until sugar is melted. Then, add cream of tartar and mix well. Next, add baking soda and mix it.
Pour the caramel syrup over the popped popcorn in the cookie sheet and mix well. (*Be careful and remember this action needs to be quick because they are very hot, sticky and harden faster.)
Mixing popcorn and caramel syrup well and make sure every popcorn is coated with caramel syrup.
Put them into an oven and bake for 1 hour at 200 F temperature. Every 20 minutes take them out and mix it.