Heat oven to 140C/120C fan/gas 1 and
line 2 baking trays with baking parchment.
Mix the dry ingredients in a large bowl.
Beat the egg with 250ml water in a jug,
then pour into the dry mixture. Combine
with a wooden spoon, then transfer to a
lightly floured work surface and knead
until you have a smooth, firm dough.
Roll the dough out as thinly as possible
and cut into squares, about 7cm. Transfer
the squares to your baking trays. Bake for
45 mins, then remove the trays from the
oven. Flip each cracker over on the tray
and return to the oven, swapping over
the shelves, for a further 45 mins. Once
cooked, remove from the oven and
transfer to a wire rack to cool. Store in
a sealed container for up to 2 weeks.