Preheat oven to 250°F and grease a couple of rimmed baking sheets.
Put 10 cups popped popcorn and 2 cups peanuts in a large bowl. Set aside.
In a large saucepan, cook 1 cup butter, 2 cups light brown sugar, ½ cup light corn syrup and ¼ teaspoon salt until it begins to boil.
Boil for 5 minutes, stirring frequently. Remove from heat and carefully stir in ½ teaspoon baking soda.
Pour hot caramel over popped popcorn and peanuts to coat. Spread over the greased baking sheets.
Bake for 40 minutes at 250°F, stirring halfway through.
Chop the 4 full size Snickers bars and stir them into the caramel corn. Bake for another 5 minutes to soften them. Then stir again to incorporate.
Cool completely. If desired, top with additional bits of Snickers bars or drizzle with melted chocolate.
Store completely cooled popcorn in an airtight container at room temperature for up to a week.
Notes
If you are using microwave popcorn, this recipe will take 3 standard size bags.Feel free to use mixed nuts instead of peanuts, it is really good that way!