If you would like to thicken the stew, you can make a cornstarch slurry by combining 1 tablespoon of cornstarch with 2 tablespoons of water and stir this in during the final minutes of cooking. Make sure the stew is simmering to activate the cornstarch. If you would like to thin the gravy (I often do this when reheating), stir in some additional vegetable broth until it reaches your preferred consistency.