Pre heat the oven to 180 C / Gas 4. Line a deep pie dish with greased baking parchment.
In a clean DRY bowl, whisk egg whites until frothy, add salt and whisk until firm. Add sugar gradually, whisking all the time until stiff and glossy.
Add the cocoa powder, cream of tartar, vinegar, cornflour and vanilla. Fold in gently and turn out into prepared pie dish making sure to mound up the sides. Put into the oven and immediately reduce heat to 150 C / Gas 2 and bake for 1 hour. Turn off oven leave oven door ajar and leave pavlova to cool in the oven.
When pavlova is cool remove parchment, pour cherry pie filling over pavlova, cover with whipped cream and add grated chocolate to finish!