Pop popcorn and remove all unpopped kernels. Pour it into a large bowl. Make the caramel by stirring together brown sugar, light corn syrup, butter, and salt in a pot over the stovetop on medium-high heat.

Allow it to come to a boil and boil for 2 minutes while stirring often. Stir in sweetened condensed milk and vanilla. Return to a boil while stirring often. Immediately remove from heat after it comes to a boil and pour over popped popcorn.

Gently stir up from the bottom and toss to fully coat popcorn. Allow it to cool for at least ten minutes before stirring in the marshmallows, chocolate chunks and graham cracker pieces (or the marshmallows and chocolate will melt). Form it into balls and place on a parchment paper-lined cookie sheet. Serve while fresh.