Laravel - Notifications - Using Mailables

If needed, you may return a full mailable object from your notification's toMail method. When returning a Mailable instead of a MailMessage, you will need to specify the message recipient using the mailable object's to method:

    use App\Mail\InvoicePaid as InvoicePaidMailable;
     * Get the mail representation of the notification.
     * @param  mixed  $notifiable
     * @return Mailable
    public function toMail($notifiable)
        return (new InvoicePaidMailable($this->invoice))