For the Meringues
To prepare the Mont Blanc recipe start preheating the oven to 120°C.
Grease a baking sheet, sprinkle with flour, and mark one 23 cm circle or ten 9 cm circles (this may require more than one baking sheet).
In large bowl, beat egg whites with salt until foamy.
Add cream of tartar and beat until soft peaks form.
Beat in 25 g sugar until mixture holds long, stiff peaks when beater is lifted.
Fold in remaining sugar and vanilla.
Place in pastry bag fitted with 1,25 cm plain tube and pipe 1 large round or 10 small ones onto prepared sheet.
Bake 1 hour or until meringue is firm to the touch.
If meringues brown during baking, reduce heat.
Transfer meringues to rack and let cool.
For the Chestnut purée
Peel chestnuts using small, sharp knife and leaving inner skin.
Preheat oven to 190°C.
Place chestnuts in shallow heatproof dish and bake 10 to 15 minutes, or until skin dries and peels off easily.
Rub nuts in rough cloth to remove skins.
Place peeled nuts in saucepan with vanilla bean and water to cover and bring to a boil over high heat.
Reduce heat, cover and simmer 25 to 30 minutes, or until very tender.
Remove vanilla bean (it may be washed and reused).
Drain chestnuts, then put through food mill or sieve, or in food processor, and purée.
Briefly boil together 175 ml water and sugar to make thin sugar syrup, then set aside to cool.
When cool, beat enough syrup into chestnut puree to make it thin enough to pipe through pastry bag but still thick enough to hold its shape.
If using canned puree, sweeten to taste, making sure it is thin enough to be piped.
Fit pastry bag with 0,3 cm plain tube and fill with purée.
For the Cream
Beat cream until stiff, and then add sugar to taste and vanilla.
Beat egg white in separate bowl until stiff peaks form, and then fold into cream.
Place cream mixture into pastry bag fitted with star tip.
Arrange meringues on serving platter and pipe chestnut puree in bird's nest shape around edge of meringue.
Sprinkle icing sugar on the Mont Blanc and chill until serving time.