Put a large, thin-walled pot on high heat –thick pots like cast iron aren’t ideal. Add three popcorn kernels to test. Put the lid on and wait until they have all popped.
Take the pot off the heat and remove the three popped kernels. Off the heat, add the oil and popcorn kernels, and shake the pot to spread them evenly. Let sit for one minute to let the kernels heat up evenly, shaking every now and again. Then, return the pot to the heat and shake every 15 seconds. Let pop until the popping slows down to almost a stop. Take off the heat and let sit for one minute in case any kernels need more time to pop.
Remove the popcorn from the pot.
Put a large, clean pot on medium heat, and add the butter and sugar. While they begin to melt, fill the sink eight centimeters deep with cold water and ice. Stir the butter and sugar until it turns into a light amber caramel. Immediately add the cream (watch out for the steam!) and take the pot off the heat and plunge the bottom of the pot into the icy water for 10-15 seconds to stop the cooking - sugar holds onto heat, and caramel can burn in a matter of seconds if you don’t. Stir the cream in to combine.
Add the marshmallows, put the pot back on the stove and turn it down to low heat. Stir the marshmallows until they are melted into the caramel.
Add the pretzels, peanuts, and popcorn and stir until evenly coated.
Spread across a flat surface lined with parchment paper. Once cool, serve immediately!