Step 1
Preheat the oven to 130C fan-forced (150C conventional) and position an oven rack in the bottom third of the oven.
Step 2
Line a large baking tray (about 40cm x 30cm) with baking paper.
Step 3
Add the egg whites to a clean dry bowl of an electric mixer. Whisk on medium until you see ribbons starting to form across the top of the mixture. Gradually add the sugar, about a tablespoon at a time, so it is well incorporated into the egg white. Once all sugar has been added, increase the mixer speed to high and whip for about 3 minutes, then turn off the mixer. Gently sift over the cornflour and then add the vinegar or lemon juice and vanilla and stir to combine.
Step 4
Turn the meringue out onto the prepared tray and, using a palette knife or spatula, spread the mixture across the baking paper in a slab, creating a few tips and dips as you go.
Step 5
Place in the oven and immediately turn oven down to 100C fan-forced (130C conventional). Bake for 45 minutes to 1 hour, then turn off the oven and leave the pavlova to finish cooking. Don’t rush this step. Leave it for at least two hours to ensure it has time to set and forms a lovely thick crust.
Step 6
To assemble, transfer the slablova to a large serving plate. Spread with the yoghurt. Top with the berries, pomegranate arils, freeze-dried strawberries and flowers.
Step 7
To make the sumac sugar, combine the sumac and sugar in a small bowl. Sprinkle some of the sumac sugar over the slablova and serve immediately with any remaining sumac sugar on the side.
