Measure out 10 cups of air popped popcorn and put it in a large mixing bowl.
In a small saucepan, whisk together the ½ cup of peanut butter and ½ cup of maple syrup over medium heat until the mixture begins to boil.
When the peanut butter/maple syrup begins to boil, pour it over the popcorn and use a large spoon or spatula to stir the mixture into the popcorn until all of the popcorn is completely coated.
Spread the popcorn out on a large sheet of waxed paper until it's cool enough to handle without burning yourself.
Grab handful-sized balls of popcorn and smoosh them together in your fist. I managed to get about 18 fist-sized popcorn balls with this recipe.