Preheat the oven to 200°C/fan 180°C/gas mark 6. Add the hazelnuts to a small baking tray and leave in the oven for 8-10 minutes, or until toasted. Remove and leave to cool.
Place the sugar in a heavy-bottomed pot over a medium heat. Without stirring, cook until it starts to melt around the edges. Use a wet pastry brush to brush away any stray sugar on the sides of the pot and swirl the pot to stop the sugar burning in spots. After 6-8 minutes, the sugar should have melted down. Once it is deeply golden (keep watching, as it can burn very quickly), add the nuts. Swirl briefly, then pour on to the baking tray. Use a rubber spatula to push out the caramel as much as you can – it will set quickly. Leave to cool completely.
Reduce the oven to 120°C/100°C/gas mark 4. Line a baking tray with greaseproof paper and draw a circle on it measuring 24cm in diameter. In a stand mixer, add the egg whites to a clean bowl and whisk until soft peaks form. Gradually add the sugar 2 tbsp at a time, beating well after each addition, for 10 minutes until the meringue is thick and glossy and the sugar has dissolved. Add the cornflour, vinegar and vanilla extract and whisk until just combined.
Spoon the meringue on to the greaseproof paper, using the circle as a guide. Smooth the sides and create a slight well in the centre of the pavlova. Use a small spatula to form grooves around the edge. Bake for 1 hour 15 minutes until the meringue is dry to the touch. Turn off the oven and leave it inside to cool completely. When completely cold, transfer to a serving plate or store in an airtight container until required.
Meanwhile, fill a small saucepan a quarter full with water and bring to a gentle simmer. Whisk the leftover egg yolks and the sugar in a medium bowl until combined, then place over the saucepan, making sure the bottom of the bowl doesn't touch the water. Add the peach purée and lemon juice and whisk often, for around 30 minutes until thick enough to coat the back of a spoon. Once the curd is thick enough, strain through a sieve into another medium bowl. Place back over the simmering water and add the butter gradually, stirring until smooth. Cover loosely with clingfilm and refrigerate until needed.
Cover the teabags with 150ml freshly boiled water and leave to steep for 5 minutes. Carefully squeeze out any access liquid, then throw the teabags away. Add the tea to a small saucepan with the sugar and stir until dissolved over a low heat. Bring to the boil for 5 minutes, stirring often, until thickened. Remove from the heat, leave to cool completely and transfer to the fridge until needed.
Using a mandolin, slice the peaches until you have several thin slices. Hand whisk the cream until soft peaks just start to form. Gently fold through about 2/3 of the curd until rippled, then pile on to the meringue base. Create shapes with the peach slices by folding or rolling, then pushing into the cream. It should create a pattern that looks like flowers. Keep adding the peach slices until the pavlova looks like it’s bursting with blooms. Drizzle over 2/3 of the syrup. Crush the praline and sprinkle on top. Decorate with the edible flowers and serve with the extra curd rippled cream and Earl Grey syrup.