Why am I getting this TokenMismatchException ?

So I'm working my way through the Build Your First App series. I'm on the final video in which, amongst other things, Jeff shows us how to use a sub-form and AJAX to update the database without a page refresh.

I'm updating a simple boolean field in the database to say whether a listed recipe has been made or not. Here's my form code:

{!! Form::open(['data-remote','method' => 'PATCH', 'url' => 'recipes/' . $recipe->id]) !!}
            <div class="form-group">
                    {!! Form::checkbox('recipe_made',$recipe->recipe_made,$recipe->recipe_made)!!}
                    {!! Form::submit('Submit') !!}
            </div>
{!! Form::token()!!}
{!! Form::close() !!}

(I added the Form::token() to try and fix the problem, no dice)

Here is the Javascript that listens for the form submission etc:

'use strict';

(function ($) {

    var o = $({});

    $.subscribe = function () {
        o.on.apply(o, arguments);
    };

    $.unsubscribe = function () {
        o.off.apply(o, arguments);
    };

    $.publish = function () {
        o.trigger.apply(o, arguments);
    };
})(jQuery);
(function () {

    var submitAjaxRequest = function submitAjaxRequest(e) {
        var form = $(this);
        var method = form.find('input[name="_method"]').val() || 'POST'; // find the hidden method field that laravel adds, otherwise default to POST
        console.log(method);
        $.ajax({
            type: method,
            url: form.prop('action'),
            data: form.serialize,
            success: function success() {
                $.publish('form.submitted', form);
            }
        });

        e.preventDefault();
    };

    //forms marked with data-remote will submit via Ajax
    $('form[data-remote]').on('submit', submitAjaxRequest);
})();
(function () {

    $.subscribe('form.submitted', function () {
        $('.flash').fadeIn(500).delay(1000).fadeOut(500);
    });
})();
//# sourceMappingURL=all.js.map

This successfully triggers and logs the correct method for the database update (ie PATCH).

However, on watching the submission in the Network tab in Chrome, I get the following 500 error:

TokenMismatchException in VerifyCsrfToken.php line 46:

This happens even if I carry out the submission as soon as I log in, so it can't be the login timing out. What's odd is that Jeff doesn't seem to encounter the error. Conspiracy! ;)

Any ideas?