Line an 8x8 inch square tin with foil or baking parchment. Making sure there is an overhang for easy extraction.
Prepare all your ingredients, weigh or measure them out. Chop up your butter, peanut butter cups and break your Oreo's up into bits. You will need to work relatively fast and having everything at hand makes it so much easier.
In a medium sized microwave safe bowl melt your peanut butter and unsalted butter together in 30 second blasts on high. To fully melt mine took 90 seconds, stir them together.
Stir in the vanilla and sea salt.
Add in the icing sugar, stir quickly to bring it all together to a soft pliable dough. It will still be warm and this is what you want.
Quickly add in your chopped peanut butter cups and stir them through the fudge mixture, because it is still pretty warm they should start to melt and become all swirled into the fudge.
Mix in half of the broken peanut butter Oreo's.
Spoon the mixture into your prepared tin and flatten it down either using your hand or the back of a spoon. Sprinkle the remaining broken Oreo pieces over the top and very gently press them into your fudge.
Cover and place in the fridge for at least 2 hours to chill and fully set.
Kept in the fridge in an airtight container this fudge will keep for 2 weeks.