Mix flour and 125ml water in a mixer until smooth, then freeze the dough for 10 minutes.
Flatten the butter into a rectangle and chill for 10 minutes.
Roll out dough, fold it over the butter, and seal the edges.
Perform two 'turns' by rolling and folding the dough before freezing for 15 minutes.
Repeat the rolling and folding process two more times.
Melt butter, lemon juice, and half the sugar in a pan.
Whisk eggs, cornflour, and remaining sugar, then combine with the hot liquid and heat until thickened.
Stir in lemon thyme, let infuse for 15 minutes, and then sieve.
Preheat the oven to 200°C.
Roll pastry to 2mm thickness and cut into 2cm by 40cm strips.
Spiral pastry around moulds, glaze with egg, sprinkle with sugar, and bake for 15-20 minutes.
Whisk cream, mascarpone, and peach syrup until soft peaks form.
Melt sugar with 2 tablespoons of water to create caramel and cool on a silicone sheet.
Blitz cold caramel into crumbs, spread on a silicone sheet, and melt in a 180°C oven for 2 minutes.
Cut the warm caramel sheet into wafers and allow to cool.
Fill cooled pastry horns with chopped peaches, lemon curd, pistachios, and a scoop of peach cream.
Garnish with a caramel wafer, peach slices, lemon thyme, and remaining pistachios.