Line a 9-inch square baking dish with parchment paper and set aside.

In a large saucepan, melt butter with sugar, heavy cream, and salt over medium heat, stirring until combined and begins to boil.

Reduce heat to low and add white chocolate chips and marshmallow fluff, stirring until smooth.

Remove from heat and fold in crushed Oreo cookies.

Pour the mixture into the prepared baking dish and spread evenly.

Refrigerate for at least 4 hours or until firm.

Cut into small squares and serve.