kirby-title.php

<?php

  // Start off with an empty $title
  $title = '';
  
  // Get all the parents (except the homepage) and reverse the array
  $parents = $site->breadcrumb()->not('home')->flip();
  
  // Iterate over the array
  foreach ($parents AS $parent) :
    
    // Add each title to a variable (with a pike as a separator)
    $title .= $parent->title() . ' | ';
    
  endforeach;
  
  // Add the site title last
  $title .= $site->title();
  
?>

<!-- Echo the title variable inside the <title> tag -->
<title><?php echo $title; ?></title>