**1) For ex: you have function getTitle() in Data.php at Namespace/Modulename/Helper**

    <?php
    
    namespace Namespace\Modulename\Helper;
    
    class Data extends \Magento\Framework\App\Helper\AbstractHelper
    {
        public function getTitle()
        {
           return "Testing";
        }
    
    }

**2) In layout.xml change xsi:type="string" to xsi:type="helper" and define helper class::methodName**

    <block class="Magento\Framework\View\Element\Html\Link\Current" ifconfig="custommodule/general/enable_footer_link" name="custommodule-link">
    <arguments>
        <argument name="label" xsi:type="string">Custom Module</argument>
        <argument name="path" xsi:type="helper" helper="Namespace\Modulename\Helper\Data::getTitle"/>
    </arguments>
    </block>