First make the bacon so that it can cool before being added to the mixture:
Heat the oven to 350 degrees.
Mix the brown sugar, chili powder, cayenne and coriander in a bowl. Make sure it is well combined.
Lay raw bacon on a strip of parchment paper or plastic wrap and sprinkle with mixture. Turn over and sprinkle liberally on both sides, pressing down slightly to make sure everything sticks. Discard the sheet.
Set the six bacon slices on a clean baking sheet that has sides to keep grease from dripping onto your oven. Bake in oven for 12 to 15 minutes until crisp. Watch closely at the 12 minute mark so as not to burn bacon. (I finished mine off in the microwave to be sure it was crisp). Remove and blot with paper towel. Set aside to cool then break up into bits.
To make the caramel corn, have everything measured and ready in advance as you need to work fast once you begin. Soften the butter slightly in the microwave. Have the bacon bits within reach.
Find two large bowls for mixing the popcorn.
Cover two baking sheets with parchment paper or use non-stick baking sheets and set aside (for cooling the corn).
Pop the raw corn in an air popper. If you don't have an air popper, check the internet for suggestions on how to microwave popcorn or use any other familiar method to pop the corn. Split up popped corn into two bowls to have plenty of room to mix the caramel sauce. Discard any unpopped kernels.
To make the caramel sauce: Combine all ingredients except for the baking soda, and place in a large pot over the stove on medium heat. Using a wooden spoon (metal will get too hot), mix ingredients to ensure that the sugar and butter have melted and all contents are well combined. Resist the temptation to touch or taste liquid...it will give you a nasty burn. Watch until bubbling liquid turns a dark caramel (it could be anywhere from 10 to 15 minutes) then immediately withdraw it from heat so that it does not burn. Stir in the baking powder. Be careful as liquid begins to double in size (hence the large pot).
Working very quickly, toss 1/2 of the bacon bits in the first bowl and cover the popped corn with half the liquid caramel. Stir together with the wooden spoon to cover as much of the corn as possible, then dump contents out onto baking sheet to cool. Break up all big clumps into more manageable pieces. Get this done fast as you need to repeat with the second bowl of corn.
Once caramel corn has thoroughly cooled, you may either devour it or store it in an airtight container. Enjoy!