1 unwaxed lemon, finely grated zest only
350g/12oz plain flour
150²µ/5½´Ç³ú caster sugar
2 sticks cinnamon
100²µ/3½´Ç³ú cornflour
150²µ/5½´Ç³ú icing sugar
icing sugar, to serve
salt
1 vanilla pod, split lengthways
175g/6oz butter, chilled and cut into cubes
2 free-range eggs, beaten
egg white, for brushing
6 free-range egg yolks
1 litre/1¾ pint whole milk