First you mix the syrup and brown sugar until it makes a soft ball in cold water.
For those who haven’t made homemade caramel corn before or worked with cooking sugar this means that you will want the mixture dissolved and then start checking it after 5 minutes or so. Get a bowl of cold water, I usually do ice, and drop a bit in. If it needs more time it will be kind of runny in the cold water and can’t really pick it up but when it’s at the right consistency you should be able to hold the syrup mixture in your fingers and make a soft, squishy ball. You can do it until it is a little harder, this will make the caramel corn crunchy when cooled if that’s what you want. We just go for the soft kind.
After you get it at that ‘soft ball’ stage take it off the stove and add your butter, baking soda and still well. At this point it will be getting foamy which is what’s supposed to happen.
Then all you do is pour it over popcorn and mix. I usually do it gradually to make it a more even coat and it helps if another person is helping so one is doing the stirring and the other is pouring but I’ve done it plenty of times on my own!
Then enjoy your homemade caramel corn!