Place the popcorn in a large bowl big enough for mixing in the cooked peanut butter caramel.
Lay out a sheet of parchment or wax paper.
In a medium pot, on medium heat, cook the corn syrup, granulated sugar, and cream of tarter.
Stirring constantly, bring the mixture to a boil and boil for 20 to 30 seconds.
Remove from heat.
Stir in the peanut butter and baking soda until an even consistency is acheived.
Pour the peanut butter caramel mixture over the cooked popcorn and stir quickly to evenly incorporate.
Using a little butter or tiny bit of water on yoru hands, quickly shape the popcorn balls into balls approximately 3 ¾-inch diameter. As you shape, lightly squeeze the popcorn together.
Place on wax paper to cool undisturbed.
Once cooled, wrap popcorn individually in plastic wrap and store at room temperature for 5 days or up to a month if frozen.