How to format output of wp_get_archives ?

I’m including an “archive” of posts to include in a sidebar on my single.php page.

How do I format it to the way I want it to look? Right now, this is the code I’m using

<?php wp_get_archives( 'type=postbypost&limit=20&format=custom' ); ?>

But it spits out the post like this in the HTML source:

<a href"link to post">post title 1</a>
<a href"link to post">post title 2</a>

How can I control the formatting so I can include my custom styles to say something like:

<div class="style for block">
<div class="style"><a href="link to post">Post Title 1</a></div>
<div class="style2">Date</a></div>
</div>
<div class="separator"></div>