Prepare your pan by lining an 8×8-inch baking dish with parchment paper, leaving overhang on the sides for easy removal later. Make sure the paper is pressed firmly into corners.
Roughly chop the Oreo cookies into chunks—aim for pieces about ¼ to ½ inch in size. Set aside about ¼ cup of the chopped cookies for topping.
Place white chocolate chips and condensed milk in a medium saucepan over low heat. Stir continuously until chocolate is completely melted and mixture is smooth—about 3-5 minutes. Be careful not to let it burn.
Remove from heat and immediately stir in the vanilla extract and salt until well combined.
Allow the mixture to cool for about 2 minutes—this prevents the Oreo pieces from melting completely when added.
Fold in the chopped Oreos (except reserved topping portion) with a spatula until evenly distributed throughout the fudge mixture.
Pour the fudge mixture into the prepared pan and spread evenly with a spatula. Work quickly as the fudge will begin to set.
Sprinkle the reserved Oreo pieces on top, gently pressing them into the surface of the fudge.
Refrigerate for at least 2 hours or until completely firm. For best results, leave overnight.
Once set, lift fudge out using the parchment paper overhang and place on a cutting board. Cut into 1-inch squares with a sharp knife.