Preheat oven to 375°F (190°C).

Combine graham cracker crumbs, sugar, and melted butter.

Press mixture into a 9-inch tart pan with removable bottom.

Bake for 10 minutes, or until crust is set.

Cool completely on a wire rack.

Sprinkle gelatin over 1/4 cup water and let stand for 5 minutes.

Heat heavy cream in a saucepan over medium heat until simmering.

Remove from heat, add chopped chocolate and vanilla, stir until melted.

Add softened gelatin and whisk until dissolved.

Beat egg yolks with 1/2 cup sugar and salt until thick and creamy.

Slowly beat in chocolate mixture until well blended.

Cover and refrigerate for 15 minutes, or until cool and on the verge of setting.

Beat egg whites and cream of tartar until soft peaks form.

Gradually beat in remaining 1/4 cup sugar until stiff peaks form.

Remove chocolate mixture from refrigerator and beat for 2 minutes.

Stir in one-fourth of the egg whites, then fold in the rest.

Spoon chocolate mixture into crumb crust and smooth the top.

Beat remaining heavy cream with confectioners' sugar until stiff peaks form.

Swirl whipped cream over filling.

Grate bittersweet chocolate over the cream.

Refrigerate for at least 2 hours.

Remove the sides of the pan and serve chilled.