Lightly grease two 20 cm shallow round cake tins and line the bases with baking paper.

Melt the chocolate.

Sift the flour and bicarbonate of soda together.

Beat the butter and sugar together until pale and fluffy.

Beat in the vanilla essence and add the eggs, one at a time.

Add a little flour to the mixture if it begins to curdle and stir well.

Fold in the melted chocolate until well blended.

Gradually fold in the remaining flour, then gently stir in the buttermilk and boiling water.

Divide the mixture between the two tins and smooth the tops.

Bake in a preheated oven at 190°C for 30 minutes, until springy to touch.

Transfer to a wire rack to cool.

Place frosting ingredients in a large bowl set over a saucepan of gently simmering water. Whisk until thickened and forming soft peaks. Remove from heat and whisk until mix is cool.

Sandwich the two cakes together with a little frosting, then do the top and sides, swirling as you do so.

Decorate the top with candied orange and lemon peel.