hat the national dish of Scotland was described in a 1615 recipe book The English Hus-wife by Gervase Markham.

Are they solely basing this on a recipe being written in a book? I'm pretty sure that doesn't prove it originated in England, mearly they were the first to document the recipe in writing.

in Scotland it could of been a common recipe that was taught to any one that cooks so there was no need to have it in text form