Sieve the flour and icing sugar into a bowl. Rub in the butter until the mixture resembles breadcrumbs. Add the egg and 2 to 3 tablespoons of the saffron infusion to bind the pastry (add a little more of the saffron infusion if necessary). Alternatively, blitz the flour, icing sugar and butter in a food processor then add the egg and 2 to 3 tablespoons o