Start by lining an 8-inch square baking dish with parchment paper, allowing some overhang on the sides for easy removal later.
In a double boiler or a microwave-safe bowl, combine 1 cup of white chocolate chips, 7 ounces of sweetened condensed milk, and 2 tablespoons of butter. Heat until fully melted and smooth.
Fold in 5 of the chopped Oreos into the white chocolate mixture until evenly distributed. Pour this mixture into the prepared baking dish and spread it evenly. Place in the refrigerator to set.
In the same manner, melt 1 cup of semi-sweet chocolate chips with the remaining 7 ounces of sweetened condensed milk until smooth and fully combined.
Remove the white chocolate layer from the refrigerator once set. Pour the semi-sweet chocolate mixture over the top, spreading it evenly. Sprinkle the remaining chopped Oreos on top.
Return the assembled fudge to the refrigerator and allow it to chill for at least three hours or until completely set. Use the overhanging parchment paper to lift the fudge out of the pan.
Cut the fudge into squares and serve!
