I'm trying to load my .phtml files in the template folder within my observer but I'm getting this error

> Invalid template file: 'VENDOR_MYModule::Category/index.phtml' in module: 'VENDOR_MYModule' block's name: 'category_0'

Here's the structure of my files
 
    app
     + code
        + VENDOR
          + MYModule
            + Block
                - Category.php
            + Controller
                + Category
                   - Index.php
            + etc
                + frontend
                    - routes.xml
            + Observer
                - CategoryObserver.php
            + view
                + frontend
                    + layout
                        - header_category_index.xml
                    + templates
                        + category
                            - index.phtml


Now the content of my `Block/Category.php` is below

    <?php
    namespace VENDOR\MYModule\Block;

    class Category extends \Magento\Framework\View\Element\Template 
    {
	    public function __construct(
    		\Magento\Backend\Block\Template\Context $context,		
		    array $data = []
	    ){
		    parent::__construct($context, $data);
	    }
	
    }

The content of my `Controller/Category/Index.php` is below

    <?php
    namespace VENDOR\MYModule\Controller\Category;

    class Index extends \Magento\Framework\App\Action\Action
    {
	    protected $_pageFactory;	

	    public function __construct(
		    \Magento\Framework\App\Action\Context $context, 
		    \Magento\Framework\View\Result\PageFactory $pageFactory
    	)
	    {
		    $this->_pageFactory = $pageFactory;		
    		return parent::__construct($context);
	    }

    	public function execute()
    	{		
    		return $this->_pageFactory->create();
    	}	
    }

The content of the `layout/header_category_index.xml` is below

    <?xml version="1.0"?>
    <page xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" layout="1column" xsi:noNamespaceSchemaLocation="urn:magento:framework:View/Layout/etc/page_configuration.xsd">
        <referenceContainer name="content">
            <block class="VENDOR\MYModule\Block\Category" name="category_items" template="VENDOR_MYModule::category/index.phtml" />
        </referenceContainer>
    </page>


The content of my `.phtml` is just a simple `<h1>Hello world</h1>`. Now in my `Observer` I'm trying to load this `.phtml` file but I can't load it and getting the error. The content of my Observer is below


    public function execute(\Magento\Framework\Event\Observer $observer)
	{			
		$layout = $this->_layout->create();
		$block = $layout->createBlock('VENDOR\MYModule\Block\Category')->setTemplate('VENDOR_MYModule::Category/index.phtml')->toHtml();		

		$this->_logger->debug("[DEBUG]::" , [$block]);
	}

But I'm getting the error as mentioned above. Any idea on how to load this .phtml file to the observer? I'm planning to write the content of this .phtml file to a .txt file. But I can't proceed since I tried outputting it but I'm still getting an error