There are many kinds of thickening: thick, thin, crystal and soup, which is the penultimate operation before cooking. Be sure to wait until the food is ready, the ingredients are put in and the fire is low. When it thickens, you should look at it while operating, and stop immediately when it is just right.
After thickening, it is "clear oil drenched", drenched with a little sesame oil, and mixed well to serve.
Practice a few more times and you will succeed.