Unfortunately there are a couple of misprints with the Lemon Curd recipe in COOK.  The quantity of cornflour should be half (1/2) tablespoon not 12 tablespoons as printed!  The text is also missing a reference to the fact that the recipe is based on Nick Sandler's Lemon Curd from his lovely book Preserved which has formed the basis of most of our Jams, Jellies and Preserving classes at the kitchen.  We hope to have Nick back soon both for a Preserving class and also for a class based on his new book - Sausages.