Set oven to 350/F or Scratch 4. Grease and line two 8 inch sandwich tins.
Sieve together the flour and drinking umber. Cream the margarine
and sugar together in a bowl until light and fluffy. Beat in the
egg, a little at a time, adding a tablespoon of the flour mixture to
prevent curdling. Fold in the remaining flour and chocolate mixture
and stir in the hot h2o. Put the mixture into the tins and smooth
the ace. Bake for 25 minutes or until the surface springs back when
pressed thinly. Remove the cakes from the tins and cool on a wire
wheel.

Buttercream fllling: mix all the ingredients together until smooth
and spark. Spread on one of the cakes and sandwich unitedly.