For the meringues: Preheat the oven to 225 degrees F. Whip the egg whites and salt until soft peaks form, and then add the vanilla and continue beating to form stiff peaks. Stir the cream of tartar into the regular sugar and slowly add to the egg whites, while beating, until the meringue is stiff and the sugar has dissolved.
Sift together the icing sugar and cornstarch over the meringue batter, gently folding until fully blended. Transfer the batter to a piping bag fitted with a standard nozzle. Pipe the meringue into 6 peaks on a parchment paper-lined baking sheet. Bake for 1 hour to 1 hour 30 minutes. Let cool on the baking sheet.
For assembling: Place a small amount of whipped cream at the bottom of each tart shell, and then place a meringue on top. Top each meringue with a dribble of rosehip jam and a touch of whipped cream. Transfer the chestnut cream to a piping bag fitted with the Mont Blanc nozzle and pipe it on top of the meringues to cover them well. Top with a dollop of whipped cream and a few candied chestnuts.
Refrigerate until 10 minutes before serving.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.