Scrape all the drippings out of the roasting pan into a medium sized saucepan, making sure to scrape the bottom of the pan to get all the brown bits off.
Add in the chicken broth.
Bring to a boil in the saucepan.
Simmer for 4-5 minutes, cooling some in a small bow to taste-test. If desired, add more chicken broth at this point.
Simmer until the gravy reaches the desired strength of flavor. Salt and pepper to taste.
Whisk the cornstarch into the water, then whisk into the gravy, slowly, only adding enough until it reaches your desired thickness.
Remove from the heat and serve in a gravy boat.
Tips: make a strong chicken broth from cubes or powdered stock to really infuse the flavor.