Break the biscuits/crackers and place them in a large bowl.
Place the butter and chocolate in a saucepan of simmering water or in a microwave. Turn off the heat. Mix in the condensed milk.
Stir the melted chocolate into the crushed biscuits until it is all coated.
Bake parchment paper on a loaf cake pan. Line all four sides. Use a spoon to press the biscuit mixture into the prepared tin. Use a spoon to scrape the chocolate from the bowl. Pour this over the biscuit cakes. Spread evenly.
Now, chill the cake. Cover the cake with tin foil, and let it cool in the refrigerator for at least one night.
Once the mixture is set, slice into pieces and enjoy!