Line an 8-inch square baking dish with parchment paper and set aside.

Combine white chocolate morsels, butterscotch morsels, rum extract, and marshmallow cream in a large mixing bowl.

In a saucepan, melt butter with heavy cream, sugar, and salt over medium heat. Bring to a boil and cook for 5 minutes, stirring constantly.

Pour the hot mixture over the chocolate and marshmallow mixture. Mix until smooth and melted.

Pour the mixture into the prepared baking dish. Let it cool and set for at least 2 hours or overnight.

Cut into bite-sized pieces and store in an airtight container. For best results, let it come to room temperature before serving.