Use @var in Twig

{# @var \App\Entity\Company company #}
{# @var \App\Entity\User user #}

{% extends 'layouts/email_layout.html.twig' %}

{% block content %}
    <p>
        Dear {{ user.firstName }},
    </p>
    <p>
        Your request to join {{ company.name }} has been approved.
    </p>
{% endblock %}