Steps
Preheat your oven to 100°C (210°F) and line a baking sheet with parchment paper.
In a clean bowl, whisk the egg white until foamy, then gradually add the sugar and cream of tartar (if using), whisking until stiff peaks form.
Pipe or spoon the meringue into a round shape on the prepared baking sheet, making a slight well in the center.
Bake for about 1.5 hours until dry and crisp. Let cool completely.
In a bowl, mix the sweetened chestnut purée with heavy cream and rum or vanilla extract until smooth and creamy.
Whip the remaining heavy cream with powdered sugar and vanilla extract until soft peaks form.
Once the meringue base is cool, fill the center with the chestnut cream and top with whipped cream.
Dust with icing sugar and place a candied chestnut on top for garnish.