Prepare an 8-inch square baking dish by lining it with parchment paper. Set aside.
Add white chocolate morsels, butterscotch morsels, rum extract, and marshmallow cream to a large mixing bowl. Set aside.
In a large, heavy saucepan, add butter, cream, sugar and salt. Bring to a boil over medium high heat, stirring frequently. Once boiling, continue to boil for a full 5 minutes, stirring constantly. Remove from heat and pour over white chocolate mixture. Using an electric mixer, blend for about one minute, until morsels are melted and mixture is smooth.
Pour mixture into prepared baking dish and refrigerate for two hours (or overnight), covered with a piece of plastic wrap.
Once set, cut into bite sized pieces and store in an airtight container at room temperature for two weeks. For freshest fudge, only cut as needed, keeping the large chunk of fudge in a ziploc bag until ready to eat.
Notes
Does butter rum fudge need to be kept refrigerated? Once it's set, you can keep the fudge at room temperature in an airtight container.
How long does fudge keep? Fudge will stay good for about two weeks. Cut off only what you will be eating right away for the best and freshest taste!
Do you need a candy thermometer to make fudge? Nope! Just make sure to let the fudge mixture come to a full rolling boil and keep it boiling for 5 minutes.