Preheat the oven
to 160'C/325'F/Gas 3. Grease and line a deep
20cm/Bin round cake tin, and grease the paper.
Sift the flour,
cocoa and baking powder into a large mixing bowl.
Add the sugar and vanilla, then gradually beat in
the oil and water to make a smooth batter. Pour the
mixture into the cake tin and smooth the surface.
Bake for 45 minutes, or until a skewer inserted into
the centre of the cake comes out clean. Leave in the
tin for 5 minutes, then turn out on to a wire rack
and leave to cool. Cut the cake in half.
For the chocolate
fudge, gently melt the margarine with the water.
Remove from the heat, add the icing sugar and cocoa,
and beat until smooth and shiny. Allow to cool until
firm enough to spread and pipe.
Place a layer of
cake on a serving plate and spread over two-thirds
of the chocolate fudge. Top with the other layer of
cake. Using a star nozzle, pipe chocolate fudge
stars over the cake. Sprinkle with cocoa powder and
chopped nuts.