i found this code snippet a couple of days ago. can´t remember where…
copy this snippet in your archive template
<?php
$year_prev = null;
$months = $wpdb->get_results( "SELECT DISTINCT MONTH( post_date ) AS month ,
YEAR( post_date ) AS year,
COUNT( id ) as post_count FROM $wpdb->posts
WHERE post_status="publish" and post_date <= now( )
and post_type="post"
GROUP BY month , year
ORDER BY post_date DESC");
foreach($months as $month) :
$year_current = $month->year;
if ($year_current != $year_prev){
if ($year_prev != null){?>
</ul>
<?php } ?>
<h3 class="archive"><?php echo $month->year; ?></h3>
<ul class="archive-list">
<?php } ?>
<li>
<a href="https://wordpress.stackexchange.com/questions/27097/<?php bloginfo("url') ?>/<?php echo $month->year; ?>/<?php echo date("m", mktime(0, 0, 0, $month->month, 1, $month->year)) ?>">
<span class="archive-month"><?php echo date("F", mktime(0, 0, 0, $month->month, 1, $month->year)) ?></span>
<span class="archive-count"><?php echo $month->post_count; ?></span>
</a>
</li>
<?php $year_prev = $year_current;
endforeach; ?>
</ul>