Prepare a 25cm square slice dish or baking tin with greaseproof paper (I always give my tin a quick spray with cooking oil then line with paper so it sticks nicely) and set aside.Using a food processor roughly crush the biscuits (or pop them in a ziplock bag and bash them a bit with a rolling pin) You want them all sizes not fine and set aside.Halve your Maltesers - *see the tip aboveIn a large saucepan slowly melt together the chocolate, butter and condensed milk, stirring often to ensure it does not catch until butter completely melted and ingredients blended together.Allow the mixture to cool slightly for at least 5 minutes, then add to this the biscuits, coconut, maltesers and cocoa powder and mix thoroughly.Pour mixture into the prepared pan and using the back of a large spoon spread it around and flatten mixture until it is completely smooth and packed tight.Put the biscuit base in the fridge to cool for 30 minutesYou can prepare this either on the stove top in a double boiler or in the microwave. Quicker and easier to use microwave.Place the chocolate in a medium sized microwave proof bowlHeat for 30 second bursts, stirring in between until the chocolate is completely melted and smooth.Add the oil to the chocolate then pour over the cooled biscuit base. (The Oil is to prevent the topping from cracking!), once it is smoothed out with the back of a spoon, give it a little shake to settle the topping evenly.Pop some more maltesers on the top, allow for the chocolate to set and slice!Store in an airtight container in the fridge.