200g plain flour
90g icing sugar
220g unsalted butter, cold diced
2 Tbsp iced water
600g caster sugar
4 egg yolks
zest and juice of 7 lemons
1 Preheat oven to 180°C. Combine the plain flour, icing sugar and 120g butter in the bowl of a food processor and pulse until a coarse crumb forms. Add the water and pulse several times until a dough forms. Roll between two sheets of non-stick paper to form a flat disc, then chill until firm.
2 Roll out the pastry to 4mm thick and line into a greased 30cm pie tin, then line with aluminium foil and baking weights. Bake for 25 minutes, until lightly golden, then set aside to cool.
3 Combine the cornflour, 280g caster sugar, eggs, yolks, zest and juice in a small saucepan and set over a low heat. Cook, whisking often, for 20 minutes, until the mixture boils and thickens, then whisk in the remaining butter. Pour into a container, then cover and chill.
4 Spoon the lemon mixture into the pastry case. Cook the remaining caster sugar with ½ cup water in a saucepan over a medium heat until it reaches hard ball (119°C). When the syrup reaches 110°C start whisking the egg whites in the bowl of an electric mixer to soft peaks. Add the syrup in a steady stream and whisk until cold. Pipe onto the lemon mixture, then lightly scorch with a kitchen blowtorch.