Special equipment: 2 (each 8-inch diameter) layer tins with removable bases, buttered.
Makes about 8 slices.
I tend to keep my kitchen stocked with very good dark chocolate buttons (70 per cent cocoa solids) as this entirely dispenses with any need to chop chocolate before melting it. Do not dream of using normal confectionary ones (except just to eat, of course).
Recipe taken from Nigella Lawson's new cookbook FEAST.