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, melt butter, then add cream, sugar, and salt. Bring to a boil over medium-high heat, stirring frequently, and cook for 5 minutes.

Remove from heat and pour over the mixture of chocolate and marshmallow cream. Use an electric mixer to blend until smooth and all morsels are melted.

Pour the mixture into the prepared baking dish and refrigerate for 2 hours or overnight until firm.

Once set, cut into bite-sized pieces. Store in an airtight container at room temperature for up to two weeks.