Only on Yummy Recipes Premium!
Yummy comes with a bookmarking feature built-in. To enable bookmarking go to Yummy Recipes at the WordPress dashboard. Check the option Enable bookmarking.
You can also allow bookmarking only for registered users with the option Allow bookmarking only for registered users.
If you have allowed bookmarking for unregistered user, and he/she registers, the bookmarks are automatically moved to the registered user.