Wait for the Appropriate Time

• Remove the gravy from the heat until you are almost ready to serve the meal. Heat causes the moisture in sauce to evaporate, which makes it thicker. If you continue to heat the gravy, it continues to thicken even if you add more liquid. Once you start thinning the mixture you must continue adding liquid and stirring to prevent it from over-thickening again. By waiting until the last minute to correct the sauce, you spare yourself a lot of extra work.

Resume Heating

• When you are ready to correct and serve the gravy, return the saucepan to the stove, and set the burner on medium-low heat. Whisk the sauce or stir it with a fork to break clumps and distribute the melting fat uniformly. The simplest way to correct over-thickened gravy is to add more of the liquid that you blended with the flour and fat to make the sauce, but there are alternative ingredients you can use, if necessary.

Add an Original Ingredient

• Milk is a common liquid in gravy. Adding more milk dilutes the flavor of the fat and flour without diluting the flavor of the sauce altogether. You can add more of the fat that you used to make the base of the gravy, such as meat drippings, if you have any left. If you do not need a lot of liquid to regain the desired consistency, you can substitute a little bit of melted butter -- no more than 2 tablespoons, in most cases. Be careful not to add too much fat, which could make the sauce too oily.

Mirror the Flavor Without Adding Fat

• Beef, chicken or vegetable stock is also a suitable thinning agent. For a gravy that contains meat drippings, stock will enhance the protein flavor without increasing the fat content. The stock does not have to come from the same type of meat that is in the gravy, though matching the ingredients yields the best results. Beef, chicken or vegetable bouillon dissolved in hot water is a suitable alternative.

Add a New Flavor

• Wine or sherry is an acceptable choice in most cases unless you are serving the gravy to children. Ideally, you should be able to thin the sauce in five to 10 minutes to prevent it from over-thickening again. But, even if you simmered the sauce for 15 minutes, only 50 percent of the alcohol in would cook off. It takes hours to cook all of the alcohol out of a sauce. While the alcohol content will likely be relatively low, it may not be a suitable ingredient for all diners.

Worst Case Scenario: Add Water

• If you're in a pinch and can't find any flavorful liquids, add water to the gravy. Use water sparingly because it dilutes the flavor. If you add drippings or butter to thin the gravy and the sauce begins to separate, stop adding fat and continue thinning it with milk, stock or water. You may need to whisk vigorously to reincorporate all the ingredients.

Stir and Serve

• Continue stirring the mixture at a medium speed as you thin it. Add about 1 teaspoon to 1 tablespoon of liquid at a time, and incorporate it into the sauce thoroughly before adding more. To prevent the mixture from over-reducing again, stir it constantly and do not leave it unattended. Remove the gravy from the heat and serve it as soon as it reaches the desired consistency. If the gravy is lumpy but is otherwise correct, pour it through a sieve before serving it to filter out the lumps.