Heat your oven to 160°C Fan/180°C/355°F/Gas Mark 4.
Cut a piece of greaseproof (parchment) paper large enough to line the base of your baking tray and draw a 20cm circle onto it. Turn the paper over so that drawn outline does not touch your meringue when added.
Ensure your bowl and whisk attachment are spotlessly clean before you add your egg whites. If you want to be totally sure wipe both with white wine vinegar, this will remove any grease etc that you can't see. Any grease at all will affect how your egg whites whisk up.
Beat your egg whites in your mixer using the whisk attachment, starting on a low setting, until they become frothy.
Add your cream of tartar and then turn up the speed to medium-high and whisk until the egg whites form soft peaks.
Turn your mixer down to a low-medium setting and add a dessertspoonful of sugar, allow the mixture to churn the sugar in for about 4 seconds before adding another spoonful and so on until all of the sugar has been used.
Turn up your mixer back up to a medium-high setting and whisk for about until the meringue forms stiff peaks. This can take a couple of minutes. Soft peaks occur when your meringue peaks but then falls back on itself, stiff peaks are the pointy ones that keep their shape.
Gently fold in your grated chocolate, cocoa powder and vanilla essence, just a few folds are enough, so as to create a marbled effect and to avoid losing air from your meringue.
Place a spot of meringue onto each corner of your baking tray then affix your piece of greaseproof paper to it, so that it is held in place.
Using your large metal spoon, blob the meringue in a heap onto the centre of the circle on your greaseproof paper, then spread out to fill the circle so that it just reaches your drawn outline.
Place your meringue into your oven and immediately turn the temperature down to 130°C Fan/150°C/300°F/Gas Mark 2.
Leave to bake for 1½ hours, until firm and set but still pale in colour, do not be tempted to open your oven door to check on your pavlova, it's very heat sensitive and can't cope with changes in temperature and you may kill it off.
After 1½ hours turn your oven off and leave the meringue to sit in your oven for another 1½-2 hours as it cools. This will ensure it continues to dry out inside.
Once out of your oven, very gently peel away your greaseproof paper.
Ensure fully cool before adding your fillings.