Prep the apples by washing them in cold water. Wipe them off and let them completely dry. By getting rid of the waxy coating on the outside, allows for the caramel to seal better to them. Remove all the stems from each apple and put a bamboo stick about ¾ of the way down into the apple.
Line a large baking sheet with the silicon mat. Wax and parchment paper will stick to the caramel.
Combine the heavy cream, corn syrup, butter, salt and brown sugar in the saucepan over medium heat. Stir constantly with a wooden spoon until the butter is melted. Once the butter has melted, if needed use the pastry brush to brush down the sides of the pan. Attach the candy thermometer to the side of the saucepan, making sure the tip does not touch down in the pan (your reading won't be accurate).
Without stirring (super important) let the mixture cook and boil until it reaches between 235°-240°. This should take between 15-20 minutes and don't worry if it takes a little longer, but be sure to use the candy thermometer as your guide. Once the caramel temp is between the 235°-240° remove from the heat and stir in the vanilla.
Don't overstir as air bubbles will form in the caramel and then they will end up on the apples as well. Allow the caramel to cool for at least 15 minutes until it is slightly thickened.
Once the caramel has thickened, it's time to dip those apples. Start by holding the wooden stick, dip the apple into the warm caramel, tilting your pot as needed to coat all sides of the apple. Lift the apple up and gently swirl it around to get the excess caramel drip off. Repeat this process with the remaining apples. Place apples on prepared baking sheets.
Immediately after coating the apples in caramel, roll in the chopped peanuts Serve and enjoy or let them sit out for about 60 minutes to set.