Mont Blanc chestnut meringues

Method

1. Heat the oven to 110°C/90°C fan/gas ¼. Line 2 baking sheets with non-stick baking paper. Draw 3 x 9cm circles on each piece of paper (6 circles in total), spaced apart. Turn the paper over on the baking sheets (the circles will show through).
2. In a large mixing bowl, use an electric mixer to whisk the egg whites with a punch of salt until foamy. Add the cream of tartar and whisk until soft peaks form when the whisk is removed. Whisk in 2 tbsp of the sugar until stiff peaks form, then use a metal spoon to fold in the remainder, along with the vanilla. Spoon meringue mounds onto the paper using the circles as a guide, then make a slight indentation in each with the back of a spoon. Bake for 1½ hours or until firm to the touch. Turn off the oven but leave the meringues inside until cool.
3. Put the sweetened chestnut purée in a small bowl and stir to loosen, adding lemon juice to taste (it should be slightly tart). In a separate mixing bowl, whisk the cream and vanilla with a balloon whisk until soft and billowy. Spoon the cream over the top of each meringue, then transfer to plates and spoon over a generous dollop of the chestnut purée. Top with the sliced marrons glacés, if using, then scatter with the grated chocolate and a little icing sugar.