Preheat the oven to 180oC. Grease and line a medium round cake tin.
Halve the pear, peel one half and chop into small pieces, removing hard inner section. Wrap the other half and put in fridge - you'll need it to decorate later.
Cream butter and sugar until light and fluffy and stir in the coffee.
Add the eggs one at a time, beating well, then fold in the flour and cocoa powder.
Fold in the chocolate, pear and walnut pieces until evenly combined.
Pour into tin - don't worry if the batter is quite runny; it is supposed to be a moist cake.
Bake for about 30-40 mins or until a cake skewer comes out clean.
When cooled slightly, turn out onto a wire rack and leave to cool completely.
Make the ganache by heating the cream until warmed through, then break the chocolate into small pieces and stir in until the chocolate has melted. Stir in the coffee.
Spread over the cake.
Peel the leftover half of the pear and cut into thin wedges. Place decoratively on cake, and brush with the marmalade to prevent browning.
Finish with chopped hazelnuts and walnut halves.
Put cake in fridge to set the ganache; serve at room temperature.