Prepare an 8x8-inch pan with wax or parchment paper that comes up the sides of the pan so you can pull out the whole slab of fudge once it sets.
Melt the white chocolate chips with the sweetened condensed milk (and salt - optional) in a saucepan over medium-low heat.
Stir in the chopped Oreo cookies, saving a few pieces to press into the top.
Pour mixture into prepared pan. Quickly spread fudge evenly with a spatula. Press extra chopped Oreo cookies on top. Let rest at room temperature until set. (Refrigerating the fudge will help it set faster.)
Pull the fudge slab out of the pan using the edges of the parchment paper. Using a warm, dry knife, cut squares. Store at room temperature in an airtight container for 5 to 7 days.
*I HIGHLY recommend Guittard vanilla milk chips - there are no waxes in them.
** This recipe has been updated due to reader feedback.