Crush the Marie biscuits into a coarse powder. Add condensed milk, aniseed myrtle, desiccated coconut and melted butter to this.
Mix everything with a fork or with your fingers.
Line the bottom of a cake tin or a rectangular tin, preferably with a loose bottom with butter paper.
Put the biscuit base in the tin and press hard. Place it in the refrigerator for about 30 minutes.
Meanwhile, make the icing with the ingredients mentioned above. You can add more or less lemon juice as per your taste. It should be of thick but spreadable consistency.
After 30 minutes, take the cake tin out and spread the icing over the biscuit base.
Put it back into the refrigerator to set.
When it is set, take it out of the refrigerator and cut into rectangular or square slices and serve.