In the Orthodox Church, there are many days (most Wed & Fri, Advent, Lent, other assorted times) that are "fasting" days, where food prep translates as vegan and/or vegetarian. The strictness of the fasts vary, but can range from 'no meat but fish & dairy OK' all the way to complete abstinence from meat, fish, eggs, dairy, wine, and oil. Ideally the food should be simple to prepare, so as not to take much time/energy/concentration.
These are some of the tried and true fasting recipes that our family uses on a regular basis....all in one place so I don't have to search for them again every time.
I have another cookbook listed with recipes we have bookmarked to try, if you'd like to browse that one as well.