Whisk/beat the egg whites until standing in soft peaks (make sure the bowl is very clean and free of all grease, or they will not whisk well). Gradually whisk in half of the sugar, continue whisking until the mixture is very stiff and glossy. Fold in the rest of the sugar, cornstarch, and grated chocolate.
Depending on how much effort and perfection you desire, you can draw forms on baking parchment and use a pastry bag (1-cm plain tip) to pipe lines. If you truly want to stack the layers of meringue on top of each other on the final cake you may want to do this - I personally just make irregular cakes by spooning the mixture onto baking parchment (on top of a baking sheet). They are usually just under an inch high and formed using a spatula, and I tend to not stack them on top of each other - this makes cutting much easier and less messy.
Bake the meringues in an oven preheated to 275 for 1.5 hours. Reverse the position of the sheets halfway through. After the allocated time, turn off the oven but let the cakes cool inside the oven with the door closed.
Peel away the parchment when cool. Melt the filling chocolate, gently spread over the meringues, and give it some time to solidify. Cover with layer of whipped cream (whip with powdered sugar if desired), and put fruit on top. Drizzle melted or grated chocolate on top as desired.
Note: Seems like it might be possible to add chopped nuts to the meringue as well? Next time... Also, if you end up with extra egg yolks they can be used for creme brulee or ice cream recipes...