For me it is a german book called “Immer schon vegan” being about stuff that always was cooked vegan from all over the world. I do not know if it available in english

Why not something like this - oldschool:

I love the idea. Maybe both sides working? Or having a fixpoint at π/2.

Is CalDAV a cloud service? Usable with some email-providers Mike mailbox.org and posteo.de