Butter and line a 15cm (6") loose bottom cake tin and set to one side.
Break the Rich Tea biscuits into small pieces, about 1 to 2 cm in size. Do not break them up too small, they should NOT be crumbs, but small pieces.
Cream the butter and sugar together until light and fluffy.
Melt the chocolate in the microwave, or in a pan set over boiling water.
Once the chocolate has melted, pour it over the butter and sugar mixture, and mix thoroughly.
Add the water the chocolate mixture, and the the broken biscuits, Mix them well, so all of the biscuits are covered and coated in the chocolate mixture.
Spoon the mixture into the prepared cake tin, and press down gently to create an even texture and surface. Place the cake into the fridge and allow it to chill for 30 minutes.
Meanwhile, make the chocolate ganache. Put the broken chocolate into a bowl. Pour the whipping cream into a pan and bring it to a simmer.
Pour the warm cream over the chocolate and mix well, stirring all the time until the chocolate has melted and you have a glossy and shiny ganache.
