Line an 8x8-inch square baking pan with parchment paper. Set aside.
Place the chocolate into a large microwave-safe bowl, and heat in 20 second intervals, stirring after each one, until melted and smooth.
Stir in the vanilla, then the sweetened condensed milk until almost combined. Fold in the chopped Oreos. The mixture will be very thick.
Spread the mixture into the prepared pan, and smooth out the top. Top with extra chopped Oreos, if desired. Refrigerate for 2 - 4 hours or overnight until completely set.
Video
Notes
Fudge can be stored in an airtight container at room temperature for 1 week, or in the fridge for 2 - 3 weeks. It also freezes well for up to 2 months. Thaw overnight in the fridge before serving.