In a medium saucepan, combine the butter, brown sugar, corn syrup, molasses and salt. Bring mixture to a boil over medium heat, stirring often. Continue to boil, stirring occasionally, until mixture reaches 265°F (this will take about 3-4 minutes after it starts to boil).

Meanwhile, preheat the oven to 225°F and place the cooked popcorn, peanuts, candy corn and marshmallows in a large, heatproof bowl.

Once the caramel mixture reaches 265°F, remove it from the heat and pour into the bowl with the popcorn; stir until well coated. (Note: The caramel mixture will be very sticky, so just stir as well as possible at this stage.)

Transfer popcorn and peanuts to a foil-lined sheet pan and bake at 225°F for 15 minutes. Remove the pan from the oven but do not stir.

Let mixture cool and then break apart into pieces for serving.