Line a 9x13 baking pan with parchment paper and set aside (note: leaving both sides higher will make it easier to pull out later).
In a microwave safe bowl, microwave peanut butter and chocolate chips in 30-second increments until smooth.
Spread evenly in the pan, and place in the freezer while you prepare your next layer.
In a stand mixer with a dough hook or paddle attachment, add marshmallow fluff, icing sugar, peanut butter, and vanilla extract. Mix until it forms a dough. (note: you can mix this by hand, you just need to be very thorough to get an even mix)
Remove pan from freezer. Working in small batches, add the marshmallow layer, and smooth out immediately. The cold chocolate will make it harder to work with as it cools the layer.
Sprinkle peanuts over the marshmallow layer, and press them in lightly, enough that they mostly stay in place. Place pan in the fridge while melting caramels.
In a saucepan, add caramels and heavy cream. Heat on medium-low until melted. Pour evenly over peanut layer (note: you may need to tip your tray from side to side to get as even of a layer as you can).
Set aside in fridge to firm up for about 5 minutes. Then, in a small bowl melt remaining chocolate chips and peanut butter. Pour evenly over caramel layer.
Place in fridge until the top chocolate layer has set, approximately 20 minutes.
Cut into 15 bars (or more).
To Store: Leftover candy pieces can be covered and stored in the fridge for 5-7 days.
To Freeze: Wrap your candy in a double layer of plastic wrap and store in a freezer-safe bag for 1-2 months.
Do not use natural peanut butter in this recipe--it is too oily and will separate. I think Jif or Skippy works great!
When lining your pan with parchment paper, leaving both sides higher will make it easier to pull out later.
You can mix the marshmallow mixture by hand if you don't have an electric mixer. You just need to be very thorough to get an even mix.