Line an 8x8-inch tin with baking paper and set aside.
Break up the white chocolate and add it to a saucepan (or heatproof bowl for microwave option) along with the condensed milk.
Place the saucepan over medium heat and stir gently until the chocolate has melted and the mixture becomes glossy. Alternatively, melt it in the heatproof bowl in the microwave, stirring every 20-30 seconds to prevent burning.
Break the Oreos into rough chunks and mix them into the fudge.
Transfer the fudge mixture into your lined tin and spread it evenly into place. A rubber spatula is great for this part if the mixture starts setting and getting thick.
Add the mini Oreos on top and gently press them in to help them stick.
Refrigerate the fudge for 4 hours until firm. Then remove from the tin, cut into squares and enjoy!