Gluten Free Chocolate Cake

A surprisingly yummy chocolate cake containing no flour!  This recipe does contain chocolate though so you will need to source some that is dairy and soya free.
110g suitable margarine
225g suitable dark chocolate
6 eggs, separated
125g fruit sugar

150g suitable dark chocolate
150g chestnut puree (optional)
30g fruit sugar
30g margarine
1) Preheat the oven to 180, and grease and line a 20cm cake tin.
2) Break the 225g chocolate up into pieces and melt in a bowl over a pan of boiling water.  Add the margarine and continue to stir until it has completely melted and mixed together.
3) Whisk the egg whites until they are stiff.  Add the sugar and continue to whisk until it is glossy.
4) Beat the egg yokes in another bowl and stir well into the melted chocolate mixture.  With a large metal spoon fold in the egg whites until they are well mixed.
5) Pour mixture into cake tin and bake for 25-30 minutes until risen.  It will still be soft in the centre.  There will be a little mixture still on an inserted skewer.  Allow to cool in tin for 5 minutes and then place on a cooling rack.
6) For the topping, melt chocolate, add chestnut puree and sugar and stir well, then stir in margarine until well mixed.  Remove from the heat, allow to cool and serve alongside the cake.