Heat oven to 180C/160C fan/gas 4.
Grease and line the base and sides of
deep, round 20cm and 15cm cake tins
with baking parchment – making sure the
paper comes a few cms above the sides.
Boil the kettle. Put half the butter and
chocolate in a pan and gently melt,
stirring. Mix together half of the flour,
sugar, cocoa and bicarb with a pinch
of salt. Whisk 2 of the eggs and 200ml
buttermilk together. Scrape the melted
chocolate mixture and egg mixture into
the dry ingredients. Add 150ml boiling
water and whizz everything together
with an electric whisk until lump-free.
Divide between the tins and bake for
40-45 mins, swapping round after
30 mins if they’re on different shelves
(the 15cm one should be done after
40 mins). To test they’re cooked, push in
a skewer and check it comes out clean.
Cool the cakes in their tins.
Repeat steps 1 and 2 again, so you
end up with 2 x 20cm cakes and
2 x 15cm cakes.
Melt the white chocolate in a bowl over
a pan of barely simmering water. Beat
together the butter and icing sugar, then
beat in the white chocolate. When the
cakes are cool, split each one in half.
Use the icing to sandwich back together
so you end up with 2 x four-layered
cakes. Sit the 20cm cake on your serving
plate and spread some more icing over
the top. Sit the smaller cake on top of
that, and completely cover with icing.
Decorate with the chocolate buttons.
If you want to add some flowers
choose something edible, like roses.
Make a posy, wrapping the stems in
a little damp kitchen paper then some
cling film, add a ribbon and add to the
cake on the day of the wedding.