Start by preheating the oven to 180° C/356° F.
Whisk the egg whites at room temperature. When the foam begins to form, gradually add the granulated sugar one spoonful at a time. Once all the sugar is incorporated, mix on high speed for at least five minutes, until the mixer leaves trails in the glossy foam and the foam peaks.
Add the starch and apple cider vinegar. Mix everything together for another minute, making sure the whole mixture is uniform and the ingredients homogenized.
Finally, add the cocoa and grated chocolate, mixing gently with a spatula, in a wide, circular, up and down motion, until incorporated.
Divide the mixture into two, one about 60% and one 40%, and pour each one into a parchment paper-lined pan, into circles of different diameters. The first will be about 25 cm (10 inches) in diameter and the second about 20 cm (8 inches).
Place the tray in the preheated oven, reducing the temperature to 140° C (285° F), and bake for about 60-85 minutes until it has a slight golden tinge and is firm to the touch. Be careful (!!!) not to leave it too long; if it burns, it will become bitter! It is best to check every 10 minutes after the first 30 minutes. Once baked, turn off the oven, open the oven door, and let the Pavlova cool in the oven with the door ajar!
Decorate with whipped cream, winter melon, strawberries, melted chocolate, etc. You'll love it! You will definitely love it!