If you can't make the nuoc mau (a bit of a fiddly proposition), there is a backup plan that actually works pretty fine, even if it doesn't produce quite the same results. Put the water, and the sugar in the saucepan without trying to make caramel, and add the meat, onion and star anise. Follow the recipe until you take off the lid. Then, crank up the heat just a little more (to raise the sugar temperature), until your sauce caramelises. It'll be less good (since the pork won't have cooked in the sauce), but it's a handy way to salvage a recipe that can be a bit tricky!