Line an 8-inch or 9-inch square baking pan with aluminum foil, leaving an overhang so you can easily remove and cut the finished fudge.

In a large microwaveable bowl, add the butter and peanut butter. Microwave for 1 minute on high, then stir. Repeat until mixture is melted and smooth.

Stir in the vanilla using a large rubber spatula or wooden spoon. Add the salt if you prefer a salty/sweet fudge and I highly recommend you do add the salt. Add the confectioners sugar and stir until completely combined. The mixture will be very thick, similar to cookie dough.

Press half the fudge into prepared baking pan. Next Sprinkle your add-ons over fudge, then spread remaining fudge smoothly over top, using a spatula. Optional, top with a few mini peanut butter cups, slightly pushing them into fudge. Cover tightly with aluminum foil and refrigerate for at least 4 hours or until firm. Cut into pieces. They taste best at room temperature, so ideally bring them back up to room temp before serving.

Fudge may be stored in an airtight container in the refrigerator for up to 1 week. You can also freeze the fudge for up to 2 months (My Mom always does this. She makes fudge in advance and takes it out for the holidays.). Fudge will thaw after 2-4 hours in the refrigerator.