Preheat the oven to 140C/fan 120C/gas 2. Line 2 baking sheets with nonstick baking paper and draw a 20cm circle on each.
Whisk the egg whites in a large clean bowl or mixer on maximum speed until stiff. Gradually add 175g caster sugar a teaspoon at a time until stiff and glossy.
Spread the meringue out on the circles to make 2 thick rounds. Transfer to the preheated oven for about an hour or until a pale cream colour and firm to the touch. Switch off the oven and leave to cool in the oven for 2 hours.
To make the filling, heat the milk in a saucepan until nearly boiling. Remove from the heat, add 50g caster sugar and half the chocolate – stir until the chocolate has melted in the hot milk.
Add the cornflour to the egg yolks in a medium bowl and mix together. Pour the hot chocolate milk over the yolks and whisk immediately until combined. Pour back into the saucepan and stir over a low heat until the custard is thick and smooth – this will take about 5 minutes. Be careful not to boil otherwise it will curdle. Set aside to get cold.
Whisk the cream until stiff, add the chocolate custard and fold together. Whisk again using an electric mixer until thick.
To assemble the torte, sit one disc of meringue on a plate. Spread with half the chocolate mixture and sit the other meringue disc on top. Spread the remaining chocolate mixture on top.
Melt the remaining chocolate in a bowl over a pan of gently simmering water. Using a teaspoon, drizzle the melted chocolate over the torte in zigzag patterns. Chill for an hour to soften the meringue slightly.
Cut into wedges and serve from the fridge.
This recipe is courtesy of 'Mary Berry's Christmas Collection' published by headline.