Customize the entry meta in the entry header

functions.php

<?php
// Do NOT include the opening PHP tag

// Customize the entry meta in the entry header
add_filter( 'genesis_post_info', 'bg_entry_meta_header' );

function bg_entry_meta_header( $post_info ) {
	
	// get author details
	$entry_author = get_avatar( get_the_author_meta( 'user_email' ), 30 );
	$author_link = get_author_posts_url( get_the_author_meta( 'ID' ) );


	// build updated post_info
	$post_info = sprintf( '<span class="author-avatar"><a href="%s">%s</a></span>', $author_link, $entry_author );
	
	$post_info .= '[post_author_posts_link] [post_modified_date before="Last updated on "]';
	return $post_info;
}