install (node.js + npm required):

configure:

add less filter to assetic configuration:

using:

twig:

{% verbatim %}{% raw %}
{% stylesheets filter='less'
    '@QcmsAdminBundle/Resources/public/less/layout.less'
    '@QcmsAdminBundle/Resources/public/less/left-menu.less'
%}
    <link rel="stylesheet" href="{{ asset_url }}">
{% endstylesheets %}
{% endraw %}{% endverbatim %}