author-box.php

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

//* Display author box on single posts
add_filter( 'get_the_author_genesis_author_box_single', '__return_true' );

//* Modify the size of the Gravatar in the author box
add_filter( 'genesis_author_box_gravatar_size', 'author_box_gravatar_size' );
function author_box_gravatar_size( $size ) {
	return '73';
}

/** Modify the author box title */
add_filter('genesis_author_box_title', 'eo_author_box_title');
function eo_author_box_title($title) {
    $title = sprintf( '<strong>%s</strong>', get_the_author() );
    return $title;
}