Lightly grease a 20.5 cm (8 in) square baking tin.
Crush the biscuits into a bowl. Sift in the icing sugar and coconut. Mix well. Melt plain/milk chocolate. Stir in the butter and add to the crumbled biscuits.
Spread the mixture into the tin and chill for a few minutes. Melt the white chocolate over hot water then spread evenly over the top.
Immediately sprinkle with toasted coconut. Leave in the fridge for 1 hour. Turn out and cut into fingers.
Tip – Remember to chill the mixture for just a few moments before adding the topping as the chocolate may separate when cut.