Preheat oven to 180C. Grease and flour a decorative ring tin.
Sift together flour and baking powder
and set aside. In a medium mixing bowl, beat together
butter, sugar and vanilla until fluffy.
Add eggs, one at a time, beating well
after each addition. Beat in cocoa. Add milk alternately with sifted dry
ingredients in three lots, beating well after each addition.
Pour into prepared tin and bake for
about 1 hour until a skewer inserted in the centre of the cake comes
out clean. Cool cake in tin for 2 minutes. Turn out on a wire rack to cool
completely.
To prepare topping: in a small bowl,
stir together sugar, vanilla and enough water to make a smooth
glaze.
Spoon over top of cooled cake. Cut up chocolate and melt with butter
in a bowl over very warm water.
Stir until smooth. Drizzle over glaze to make a
decorative two-toned pattern. Stand until set.