For poached peaches, bring wine and sugar to the boil in a deep-sided frying pan over medium-high heat, stirring to dissolve sugar. Add peaches, cover with a round of baking paper, reduce heat to low-medium and simmer until peaches are tender (15 minutes). Strain peaches well, return liquid to pan and reduce over high heat until thick and syrupy (5-7 minutes). Add peaches and cook for a further 2 minutes or until peaches are well glazed. Transfer to a container and refrigerate until required. Poached peaches will keep refrigerated for 2-3 days.
For pavlova, preheat oven to 180C. Whisk eggwhite in an electric mixer until soft peaks form, then gradually add sugar, whisking continuously, until smooth and glossy and sugar has dissolved (see note). Sift cornflour over, add vinegar and stir to just combine. Spoon onto an oven tray lined with baking paper and spread into a 20cm round. Bake until crisp on the outside and starting to crack (20 minutes). Turn off oven and leave pavlova in oven to completely cool (about 1 hour), then break into shards. Pavlova will keep stored in an airtight container in a cool, dry, dark place for 24 hours.
Whisk mascarpone, cream, icing sugar and amaretto in a bowl until soft peaks form and refrigerate until required.
Spoon poached peaches and syrup into serving glasses, top with cream mixture, top with a piece of pavlova, scatter with chopped hazelnuts and serve.
Note To test that the sugar has dissolved when
making pavlova, rub a little mixture between your fingertips: if it
feels gritty, continue whisking until it's smooth.