There have been mentions of various restaurants around beautiful Lago Zirahúen, not far to the west of Pátzcuaro. I recall reading about La Troje de Ala many years ago in a "Mexico on $35 a Day"
A friend says it's relatively expensive by local standards. I'm wondering if it's worth a visit.
So far, the most detailed description I've found by Googling is here: http://tinyurl.com/TdeAla