Prepare an oven-sized baking tray. Layer it with parchment paper. Using a 28 cm (11 inch) diameter cake tin, draw a circle on the parchment paper. Set aside.
Preheat the oven to 120°C (248F).
Fit stand mixer with a whisk attachment. You can also use hand mixer and a large bowl.
Place egg whites in a bowl of the stand mixer. Measure out the sugar into a separate bowl.
Start beating the egg whites, first on low speed slowly increasing to medium. Beat until the egg whites stiffen (approx. 3-5 minutes).
Keep the mixer on medium speed and start adding the sugar. Add a tablespoon of sugar at a time (make sure that you don't increase the amount of sugar added), mixing for 30-40 seconds after each tablespoon [see notes in section 'Do's and Don'ts']. When all sugar is added, mix everything on medium speed for 2 more minutes. Add vanilla, potato starch and vinegar and mix everything on medium speed for 1 more minute.
Using a spoon, scoop out mixed egg whites to the centre of the previously drawn circle. Gently press the middle so that it creates a little dip and, using a spatula, raise up the edges of the pavlova.
Place the pavlova in the pre-heated oven. Bake for 30 minutes in 120°C (248F). Next, decrease the temperature to 100°C (212F) and dry the pavlova for 3 more hours.
After this time, take the pavlova out of the oven and let it cool completely before decorating and serving.