Preheat your oven to 350°
Clean a large mixing bowl or the bowl of a stand mixer very well and dry it completely
Add 5 egg whites and 1/2 teaspoon of cream of tartar into the bowl and mix with an electric hand mixer or stand mixer at medium speed until soft peaks begin to form
Once soft peaks begin to form, start adding the superfine sugar a tablespoon at a time while continuing to mix on medium speed until it has all been added and stiff, glossy peaks have formed
Once stiff peaks have formed, turn off the mixer and sift 2 teaspoons of cornstarch and 2 tablespoons of cocoa powder into the bowl
Turn your mixer on for only 1-2 more seconds to very quickly incorporate the dry ingredients (do not overmix)
Add the roughly chopped chocolate and very gently fold just a few times to incorporate
Transfer the mixture onto a baking sheet lined with a sheet of parchment paper and shape as desired
Transfer onto the center rack of a preheated 350° oven and immediately reduce the ovens temperature to 300°
Bake for 1 hour and 15 minutes
When the full baking time has elapsed, turn your oven off and open the oven door slightly
Allow the pavlova to cool fully before removing it from the oven
Top with fresh whipped cream and chopped chocolate