window.wp.hooks.addFilter(
    'editor.PostFeaturedImage',
    'myplugin/myhook',
    function( original ) {
        console.log (original);
        return function() {
            return (
                window.wp.element.createElement(
                    'div',
                    { key: 'outer' + Math.random() },
                    [
                        'Prepend above',
                        _.extend( original( {} ), { key: 'my-key' } ),
                        'Append below'
                    ]
                )
            );
        }
    }
);