Mmm the Shepard pie sounds lovely. Another comment that makes we wish we had an oven although I should try the in the solar oven..
Huh, sorry to hear you've had issues growing them, But stoked this year's crop looks good. Haha. I imagine canned potato being the YUCK you described. Not tickled by the Idea.
My 2 cents on ground temps is that is would be cool below the frost line. It should stay at a constant 55 f or 15 C or so. The earth stays cool if you just keep diggin.