Line 8x8-inch pan with parchment/foil, leaving an overhang for easy removal. Cut butter into tablespoons. Coarsely chop the Oreos.
Melt butter, white chocolate, salt, and sweetened condensed milk together in a thick-bottomed, nonstick pan on the lowest heat setting. Constantly stir with a heat-resistant spatula, scraping the sides and bottom. Do not raise the heat—patience ensures a smooth mixture.
Once ingredients are melted, take the pan off the heat. Mix in the vanilla. Gently fold Oreos into the mixture.
Pour mixture into prepared pan. Using a spatula sprayed with cooking spray, smooth fudge into an even layer. Crush remaining 2 Oreos and sprinkle over top, pressing them gently into the surface. Cover and refrigerate for 3–5 hours, or until the fudge is set and firm.
Lift the fudge out using the parchment overhang. Cut into small pieces with a sharp knife warmed under hot water and dried.
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Notes
Note 1: Use high-quality chocolate for better Oreo Fudge taste; recommended brands: Ghirardelli® and Guittard® (not sponsored).Note 2: Use full-fat sweetened condensed milk, not evaporated milk.Storage: This fudge is best within 1–2 days. For longer storage, keep it as a tightly wrapped block in the fridge or freezer. Once cut, wrap pieces individually and store at room temperature.