The actual quote from the cookbook says: "The use and vertues of these two severall kinds of Oate-meales in maintaining the Family, they are so many (according to the many customes of many Nations) that it is almost impossible to recken all;” and then proceeds to give a description of “oat-meale mixed with blood, and the Liver of either Sheepe, Calfe or Swine, maketh that pudding which is called the Haggas or Haggus, of whose goodnesse it is in vaine to boast, because there is hardly to be found a man that doth not affect them".

He specifically mentions multi-national origins for recipes, and never claims this one to be of English origin. How does one deduce that just because the recipe appears in an English cookbook that it must be of English origin? I would think that real historians would be all over that.