I’m using Hemingway, and it can be done.
In the WP control panel, under Options > Reading, set Blog Pages > Show at most # pages to your desired number (I’ve just set it to 10).
As I’m using WP as a photoblog with the Hemingway theme, I like my index page to show only the most recent post.
Here is the first few lines of my index.php
?php get_header(); ?>
<div id="primary" class="twocol-stories">
<div class="inside">
<?php
// Here is the call to only make two posts show up on the homepage REGARDLESS of your options in the control panel
query_posts('showposts=1');
?>
<?php if (have_posts()) : ?>
<?php $first = true; ?>
<?php while (have_posts()) : the_post(); ?>
………..
The key line is ‘query_posts(‘showposts=1′);’
Not sure what theme you’re using or how it is done outside of hemingway, but it’s how I’ve just managed to do it 🙂