Preheat your oven to 350°F (175°C). It’s important to have your oven ready before you start making the caramel, as you’ll want to bake the mix right after.
Prepare your baking sheet by lining it with parchment paper or a silicone baking mat. Avoid using foil, as it can lead to sticking. Set this aside for later.
In a large bowl, combine the popped popcorn, peanuts, and pretzels. Make sure to toss them gently to mix evenly. This combination will form the base of your snack mix.
Next, in a medium saucepan over medium-high heat, add the unsalted butter. Allow it to melt completely, swirling occasionally to ensure it doesn’t burn.
Once the butter is melted, stir in the brown sugar and light corn syrup. Increase the heat to medium-high, stirring often until the mixture begins to boil.
As soon as the mixture reaches a boil, reduce the heat to low. Allow it to simmer for about two minutes without stirring. This will help it thicken nicely.
After two minutes, remove the saucepan from the heat and carefully stir in the salt and vanilla extract. The mixture will bubble slightly; that’s normal!
Add the baking soda to the caramel sauce, stirring well until it becomes light and fluffy. This step is key to achieving that perfect texture.
Pour the caramel sauce over the popcorn mixture in your large bowl. Quickly stir everything together to ensure the caramel coats all the pieces evenly. Be careful; the caramel may be hot!
Spread the coated popcorn mixture onto your prepared baking sheet. Bake in the preheated oven for about two minutes.
After two minutes, remove the sheet from the oven and stir the mixture thoroughly. Then, place it back in the oven for another two minutes. This helps to set the caramel.
Once done, take it out and allow it to cool completely on the baking sheet. This cooling process allows the caramel to harden and bind the mix together.
Once cool, add the Reese's Pieces and Reese's Peanut Butter Cups Minis to the mix. Gently break it into pieces and serve immediately.
Store any leftovers in an airtight container to keep them fresh and crunchy.
