SC - Help with 1650s+ info

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Good Gentles, 

A lady in the Barony I just moved into is doing a very, very late period 
feast. She's including hot chocolate from a receipe book in the 1660s. As she 
had a few vegetable dishes left blank, I suggested a roasted potato dish to 
please the fighting crowd the event is aimed at. I'm afraid the suggestion 
met with a less than warm response.

My questions are:

Does Sir Digbie talk about potatoes in his book? Do any books of that time?

An argument could be made that potatoes aren't Elizabethan, but what about 
this late date?

When is the first cookbook that contains a receipe for potatoes? 

Your assistance is gratefully appreciated!
Rosalyn MacGregor
(Pattie Rayl)