Prepare an 8x8 cake pan by lining with parchment paper or foil.
chocolate layer:
Combine chocolate and peanut butter in microwave safe bowl. Microwave for 2 minutes at 50% power, stir, and repeat until just melted. Pour into prepared pan and use a rubber spatula to spread an even layer on the bottom. Transfer dish to freezer to harden.
caramel layer:
Remove the pan from the freezer and pour the caramel over the chocolate. Spread to cover. Then sprinkle the peanuts on top. Return the pan to the freezer.
fudge:
Combine the butter and peanut butter in a large microwave safe bowl (I used glass) and cover with a large plate. Microwave for 2 minutes on high. Stir and microwave on high for 2 more minutes. Be extremely careful as this mixture will be very hot and melted.
Add the powdered sugar and stir well until everything is fully combined and smooth. Add the vanilla and stir to combine.
Transfer the warm fudge to the pan and use the spatula to make an even layer. If it gets hard to spread, use the spatula to pat it down - this will give you a nice smooth surface if you pat fast enough.
Cut a square of parchment paper the size of the fudge and cover completely (you want the parchment touching the fudge). Refrigerate refrigerate until cool, about 1-2 hours.
To cut, lift fudge out of pan and transfer to a cutting board. Pull away parchment. To get a nice clean cut, I boil water and add it to a tall glass. Then I set my largest sharpest knife sit in the hot water. Before every slice, wipe the knife and any excess fudge off for a clean cut, then repeat for each cut.
Cut into 16 two inch pieces for full dessert sized portions or 64 one inch pieces if you prefer bite sized treats.
Notes
Nutritional information based on one square inch piece.
Recipe Tips:
Peanut butter - I used crunchy peanut butter with no added sugar. There's enough sugar in this fudge that I personally feel a sweetened peanut butter would be too much. I also really liked the little chunks throughout.
Peanuts - Easy method is to buy roasted peanuts. Alternatively, you can use whole raw peanuts, slightly toast in a pan on the stove over low heat while constantly shaking to prevent burning, and then transfer to a clean towel to rub the skins off the roasted peanuts.
Caramel sauce - Easy method is to buy a jar. Otherwise, I highly recommend you try making your own homemade Salted Caramel Sauce.
Fudge can be stored in an airtight container at room temperature for up to a week, however if your house is warm the fudge will be very soft and better kept in the refrigerator. Alternatively, you can store it in airtight freezer bag in the freezer for longer.