fatal error call to undefined function in header.php

Just updated everything (wordpress, portfolio press, all plugins) and followed the suggestions in portfolio press to set up the new verion correctly.

I have a child theme that appears to be working for the most part, but its header.php is causing the following message to appear on my site (and nothing else): “Fatal error: Call to undefined function of_get_option() in /home/karluschold/karluschold.com/web/wp-content/themes/ku2/header.php on line 50”
Line 50 reads “<?php if ( of_get_option(‘logo’, false) ) { ?>”

I thought maybe it was bad lines in my pre-update based header.php, so I remove it and just copied the header.php directly from Portfolio press into my child theme to start making my changes from the beginning again. However, while this file work in Portfolio Press it causes the same error in my child theme.

Is there somewhere I need to go to define this function and if so, what/how should it be defined?
“of_get_option” does not appear in any other files in Portfolio Press or my child theme (except Footer.php which appears to cause a similar error if I remove header.php all together.).