Hi there,

The featured page widget strip all code tags from the content and excerpt field, and have a custom set excerpt length. 

I think the easiest option in this case is to add 2 Visual Editor widgets to the page builder columns. Add your heading and text to the bottom widget and in the top visual editor widget add the following code in the text tab (not the visual tab).

<div class="post-item page">
    <a href="#-link-to-page-here" class="post-item-image">
        <img src="#image-link-here">
        <div class="overlay">
            <div class="vertical-center">READ MORE</div>
        </div>
    </a>
</div>

Please add your image link to the src attribute of the img tag and the page link in the href attribute of the a tag.

If you have any questions, feel free to ask