Simfony2-Twig: Render only a single part of a template - php

Question

I have a homepage wich dynamically loads a bunch of "posts" (similar to facebook wall).
There is the option to follow a post, but when someone clicks on the follow button, which has a counter on following people, I need to reload all the homepage to update this value. How can I update just the part corresponding to the post? Actually the post is in an extern hmtl.twig file which I render from the homepage code:
<div class="row">
<div class="col-md-6">
{% for sueno in suenos %}
{% if loop.index0 is even %}
{{ render(controller('SuenoBundle:Default:suenoFrontend', { 'sueno': sueno } )) }}
{% endif %}
{% endfor %}
</div><!--/col-md-6-->
This is the controller:
public function suenoFrontendAction($sueno)
{
return $this->render('SuenoBundle:Default:suenoFrontend.html.twig', array(
'sueno' => $sueno));
}
This the post html file:
<h4 class="text-center nombre-usuario">{{ sueno.usuario.nombre ~ ' ' ~ sueno.usuario.apellido }}</h4>
{% if sueno.necesitaAyuda == 1 %}
<p class="text-center texto-sueno"><img src="{{ asset('bundles/estructura/images/SOS.png') }}" width="25" height="25" alt="SOS" /></p>
{% endif %}
{% if sueno.rol == 'foto' %}
<img src="{{ asset('upload/images/' ~ sueno.fotoLink) }}" class="img-responsive img-thumbnail" alt="Responsive image">
{% elseif sueno.rol == 'video' %}
<div class="video-container"><iframe src="{{ sueno.linkVideo }}" frameborder="0" allowfullscreen=""></iframe></div>
{% endif %}
<h4 class="text-center titulo-sueno">{{ sueno.titulo }}</h4>
<h4 class="text-center quepido-sueno">{{ sueno.quePido }}</h4>
<p class="text-center texto-sueno info">{{ sueno.texto }}</p>
<br>
<div>
{% set size = sueno.usuariosColaboradores | length %}
{% set size2 = sueno.usuariosSeguidores | length %}
<p class="text-center opciones-sueno">
<img src="{{ asset('bundles/estructura/images/colaboradores.png') }}" width="20" height="20" alt="Colaboradores" /> {{ size }}
<img src="{{ asset('bundles/estructura/images/punto.png') }}" width="5" height="5" alt="punto" />
<img src="{{ asset('bundles/estructura/images/seguidores.png') }}" width="20" height="20" alt="Seguidores" /> {{ size2 }}
<img src="{{ asset('bundles/estructura/images/punto.png') }}" width="5" height="5" alt="punto" />
<img src="{{ asset('bundles/estructura/images/compartir.png') }}" width="20" height="20" alt="Compartir" />
</p>
</div>
<hr>
Here you can see the action correpsonding to follow a post(its in the previous code, I remark the line):
<img src="{{ asset('bundles/estructura/images/seguidores.png') }}" width="20" height="20" alt="Seguidores" /> {{ size2 }}
size2 value is the one to update. the controller called when clicking here is this(and where I suppose the failure is):
public function seguirAction($suenoid)
{
$em = $this->getDoctrine()->getManager();
$usuario = $this->getUser();
$sueno = $em->getRepository('SuenoBundle:Sueno')->findOneBy(array('id' => $suenoid));
$usuario->getSuenosSigue()->add($sueno);
$em->persist($usuario);
$em->flush();
// $suenos = $em->getRepository('SuenoBundle:Sueno')->findBy(array('usuario' => $usuario->getId()));
//esto hay que cambiarlo entero para conseguir los sueños apropiados
//return $this->render('EstructuraBundle:Home:home.html.twig', array('suenos'=> $suenos , 'usuario' => $usuario));
return $this->render('SuenoBundle:Default:suenoFrontend.html.twig', array(
'sueno' => $sueno));
}
The thing is that when this render happens, the post fills the full page.
What I want is just to re-render this post in the homepage