Inject HTML to a Mailgun template variable

I have created a main template in Mailgun, with a {{body}} variable within the HTML code.

Sending emails using this template works fine when passing a simple string to the body variable, but I would like to be able to pass some HTML. Something like that:

    return mailgun.messages().send({
        from: fromEmail,
        to: toEmail,
        subject: subject,
        template: "main",
        "v:body": "<p>This is a <strong>parsed</strong> HTML paragraph.</p>",
    }, (error, body) => {
        console.log(body);
    });

The email gets sent but the body HTML is not rendered and appears as full text in the email (as in showing the tags).

Is there a way to inject HTML so that it is actually rendered?