Cook the tagliatelle as per the packet instructions, then drain and run under cold water to stop from cooking any further.
Spray a frying pan with low calorie cooking spray and set on a medium heat.
Fry the beef strips, in batches, for 2-3 minutes until browned but still tender. Remove and put to one side.
Add the onions and mushrooms to the frying pan and cook for 3 minutes until softened.
Add the stock pot, water, balsamic vinegar, black pepper, salt and Dijon mustard to the frying pan and cook for 6 minutes until reduced slightly.
Add the beef back into the pan and cook for 2 minutes, then add the cream cheese and mix well.
Add the tagliatelle and spring onions to the beef and cook for 2-3 minutes until pasta is hot. Serve.