Preheat oven to 140C/ 275F/ GM1
Cut a piece of baking parchment to fit your baking sheet. Draw a circle onto the centre of the parchment using a regular sized side plate as a template. Flip the parchment over so the pencil marking is on the reverse
Weight the sugars into one bowl and stir to combine
Put the egg whites into a medium sized bowl and begin to whisk, using electric beaters, until just stiff
Add the sugar, 1 teaspoon at a time, whisking continuously, until all of the sugar has been added. This process will take around 5 minutes, but the meringue will be a much better texture than if you add it all in one go
Add the vinegar and cornflour and whisk for a further minute until fully incorporated
Spoon the meringue into a piping bag fitted with a suitable nozzle (I used a Wilton 4C) and pipe a meringue nest onto the template - begin by piping a dot onto the template you have drawn (12 0'clock). This is the centre of the nest. Next, in one continuous motion, go around the dot twice to make a bigger circle, and then go around again on top of the outer circle to make the sides. In the same way, pipe another nest onto the template directly opposite the first nest (6 o'clock). Add a nest at 3 o'clock and one at 9 o'clock. Finally, pipe 4 more nests in between the first 4 to join up the meringue and complete the circle (the nests need to be touching). Use any extra meringue to fill in/ join/ decorate the wreath or to add extra height to the nests.
Put into the oven, turn the heat down to 120C/250F/ GM ½ and let cook for 30 minutes. After 30 minutes, turn the heat down to 100C/ 210F/ GM ¼ and cook for a further 30 minutes
Try to peel the parchment away from the meringue - it should easily come away. If so, remove the meringue from the oven and let cool completely. If not, allow to cook for 5-10 more minutes and test again
Once cool store in an airtight container at room temperature until ready to assemble and serve