Preheat oven at 225˚ F. Place parchment paper on baking sheets, and trace 3 to 3½ inch circles (as your guide for the pavlovas). Flip parchment paper over (traced circles should be facing down towards the sheet pan).
Using a stand mixer, whisk the egg whites until soft peaks form. Slowly add in the sugar; continue whisking (8-10 minutes), until egg whites become stiff and the mixture is smooth and glossy.
Combine cornstarch, vinegar, and vanilla in small bowl; gently fold into the meringue mixture, until fully incorporated but do not over mix, about 5-6 seconds. Drizzle the melted chocolate into the meringue, and with a spoon, gently swirl chocolate a few times without mixing!
Spoon or pipe the meringue in the middle of each traced circle (for extra texture, free form with a spoon). Use the back of a spoon to push outwards; creating a well with the meringue for the filling.
Bake for 1 hour and 15 minutes then turn oven off and without opening the door; let meringue sit in the hot oven 1-2 hours. The outside will be dry and crisp and the inside will still be marshmallow soft.
Place mixing bowl, wire whisk or whisk attachment, and cream in the freezer for 10-15 minutes.
Beat very cold whipping cream with sugar in the cold bowl for 2½ minutes or until whipped and spreadable. Pipe cream onto the pavlova ‘s and dust with cocoa powder and finish off with chocolate shavings. Enjoy!