app.js

var express = require('express')
  , cookieSessions = require('./cookie-sessions');

var app = express();

app.use(express.cookieParser('manny is cool'));
app.use(cookieSessions('sid'));

app.get('/', function(req, res){
  req.session.count = req.session.count || 0;
  var n = req.session.count++;
  res.send('viewed ' + n + ' times\n');
})

app.listen(3000);

cookie-sessions.js

module.exports = function(name) {
  return function(req, res, next) {
    req.session = req.signedCookies[name] || {};

    res.on('header', function(){
//      res.signedCookie(name, req.session, { signed: true }); 
       res.cookie(name, req.session, { signed: true });
    });

    next();
  }
}

Fixed a bug from the original, which is more likely a typo, yet it blocked the startup.