110g/3¾oz dairy-free margarine, plus extra for greasing
225g/8oz dairy-free dark chocolate, with at least 70 per cent cocoa solids
6 eggs, separated
125g/4oz/¾ cup sugar
Topping:
150g/5oz dairy-free dark chocolate, with at least 70 per cent cocoa solids
150g/5oz chestnut purée
30g/1oz sugar
30g/1oz dairy-free margarine
Method
Preheat the oven to 180°C/350°F/Gas 4. Lightly grease a deep 20cm/8in cake tin with dairy-free margarine and line the base with a circle of non-stick baking parchment.
Break the chocolate into small pieces and place in a large heatproof bowl. Rest the bowl over a pan of gently simmering water, making sure that the bottom of the bowl does not touch the water. Stir from time to time until the chocolate has melted. Add the margarine to the bowl and continue stirring occasionally until it is completely melted and mixed in with the chocolate. Remove from the heat.
Put the egg whites in a mixing bowl and whisk using a hand-held electric whisk until they form stiff peaks. Add the sugar and continue whisking until they form glossy peaks.
Lightly beat the egg yolks in another bowl, then stir into the melted chocolate mixture until well blended. With a large metal spoon, carefully fold in the whisked egg whites until they are thoroughly mixed in.
Pour the mixture into the prepared cake tin and bake in the hot oven for 25–30 minutes until risen and cooked around the sides but still slightly soft in the centre. Insert a skewer into the middle of the cake and if there is only a little of the cake mixture sticking to it, the cake is ready. Take the cake out of the oven and leave to cool in the tin for about 5 minutes, then transfer to a wire rack and leave to cool completely.
Meanwhile, prepare the topping. Melt the chocolate as above. Add the chestnut purée and sugar and stir well, then stir in the margarine until thoroughly blended. Remove from the heat, leave to cool and serve with slices of the cake.
Recipe by Grace Cheetham at https://www.gracecheetham.com/flourless-chocolate-cake