Preheat oven to 150°C. Using a piece of kitchen paper and a little lemon juice, wipe around the interior of a large bowl or the bowl of freestanding mixer, along with the whisk attachments to ensure everything is completely grease free otherwise egg whites will not whip up properly. Line an oven tray with parchment paper or reusable silicone sheet.

Whisk the white until they reach soft peaks. Now add sugar, a tablespoonful at a time until all sugar is incorporated. When you have reached the correct consistency whites will have increased significantly in size, be glossy and stiff peaks remain when beater is removed.

Add the cornflour, vinegar and rosewater into the whites and fold in using a metal spoon or spatula. Go gently so you don not knock the air out of the whites.

Dollop the mixture onto the lined baking tray and form into a large fat disk. If using parchment paper add a dab of meringue to each corner of the paper using it to stick the paper to the tray

Tip the rhubarb and sugar into an oven proof dish. Cover with foil. At this stage both pav and rhubarb can go into the oven. Put rhubarb on top shelf and pav on lower. Allow to cook for 1 hour.

When it has had its hour in the oven switch off the oven remove the rhubarb but leave the pavlova to remain in the switched off oven to cool completely.

When Remove the rhubarb from the syrup with a slotted spoon into another bowl and tip the syrup into a suitably sized saucepan. Place on the hob over a high heat and allow to reduce by half. Then set aside to cool. Using a fork mix the soft rhubarb into a stringy mush.

When pavlova has completely cooled. Whisk the cream until softly whipped. Turn the now cooled pavlova out onto a cake stand or serving plate. You want the flat bottom to be facing up. Combine the white chocolate and stringy rhubarb. Dollop this on the upended pav base. Then drizzle the whole pav with a little rhubarb syrup (reserve some for adding at the table), sprinkle over rose petals and the remaining white chocolate.