You might be able to adapt the recipe at the site below using leftover mashed potatoes. I'm sure she didn't use the pastrami, either but check it out.

Here is a link that might be useful: Turkey roll

Here's another to check out. It calls for cooked rice but that could be switched with potatoes.

Here is a link that might be useful: Turkey Coulibiac

ty ty I knew it!!!!!!!!!!!! I knew someone here would know about this recipe...........I even thought about the pre-made Puff Pastry Sheets ...............wow ty !!! Im gonna try both- ty again Nancy

Hope they work!

OK- I used Bisquick- as the bread and stuffed it w/ leftover turkey stuffing and gravy--------------what a treat ty everyone!!!!!!!!!!!!!!!!!!!!!!! NJ

I was going to suggest that it was a Thanksgiving version of a Runza.
Perhaps Grandma used a yeast dough? Was Grandma German? Or did she come from Nebraska?

Here is a link that might be useful: runza