How to have an url link within toggled text ?

Hi,
The template I use as a toggle shortcode.

[toggle title="My title"]All the text I want to hide or show clicking the title[/toggle]

but…. I can’t have a link within the toggle texted. That is:

[toggle title="My title"]All the text I want to hide or show clicking the title <a href="http://my_link">READ MORE</a>[/toggle]

can NOT works, as toggled text is not html considered.

I had a look to toggle’s plugins and the same happens.

QUESTION
Anyone can help and tell how I can include a link within the toggled text ?

Maybe adding a parameter [ toggle title=”My tile url=”http://my_url ]

but I have no idea of coding a function.

This is the code of template’s shortcode function

function toggle_shortcode($atts, $content = null) {

    extract(shortcode_atts(
        array(
            'title' => 'This is your title'
    ), $atts));

    $output = '<div class="toggle">';
    $output .= '<a href="#"><span>+</span>'.$title.'</a>';
    $output .= '<div class="box">';
    $output .= do_shortcode($content);
    $output .= '</div><!-- .box (end) -->';
    $output .= '</div><!-- .toggle (end) -->';

    return $output;
}
add_shortcode('toggle', 'toggle_shortcode');

Thank you