Step 1Heat the oven to 375 degrees. Spread the peanuts on a baking sheet and roast them until they're slightly colored, about 12 to 20 minutes, turning every so often. Let them cool.
Step 2Melt the butter in a medium saucepan over medium heat, then add the brown sugar, honey, molasses, corn syrup, baking soda, vanilla and salt. Stir, allowing the mixture to come to a boil. Reduce the heat to medium, and boil gently without stirring, about 3 minutes (or until the mixture registers 285 degrees on a candy thermometer--soft-crack stage).
Step 3Reduce the oven temperature to 250 degrees. Line a baking sheet with parchment paper.
Step 4Place the popcorn in a large, heat-safe bowl. Slowly pour the syrup over the popcorn. Stir and toss, adding in peanuts at the same time, and toss to coat as best you can.
Step 5Turn the popcorn onto the baking sheet. It will not look thoroughly coated with caramel at this point, but that will take care of itself as it bakes and dries.
Step 6Bake the popcorn, tossing and shuffling it every few minutes, for about 20 minutes.
Step 7Cool and break the popcorn into serving-size pieces. (This keeps for about three days. You may freeze the cooled popcorn on large baking sheets, which will keep it crisp and reduce clumping. Once frozen, place portions in paper bags and store it in the freezer. The popcorn will come out of the freezer crisp, but it begins to get soggy if not eaten right away.)