Meringues:
Preheat the oven to 250°F (120°C)

Beat the egg whites with the cream of tartar and sugar until stiff peaks form.
The result should be firm (like a bird’s beak).
Fold in the cornstarch with a spatula, which helps keep the center tender.

Draw 6 circles of 4″ (10cm) in diameter on parchment paper with a pencil.
Put the egg whites in a piping bag and cover the circles.

Bake for 1 hour to 1 hour 15 minutes. Let cool completely.

Chocolate Chantilly:
Put the chocolate in a bowl.
In a saucepan, bring the cream to almost boiling point.
Pour the cream over the chocolate and mix with a whisk until the chocolate is melted and the mixture is smooth.
Cover and refrigerate for at least 4 hours or until the mixture is very cold.
Using an electric mixer, whip the chilled chocolate cream at high speed.
Stop beating as soon as the cream is firm and loses its shiny appearance.
Use immediately.