There are several ways to thicken gravy, depending on your preference and the ingredients you have on hand. Here are some common methods to thicken gravy:
Roux: A roux is a mixture of equal parts flour and fat (usually butter) that is cooked together to form a paste. To use a roux for thickening gravy, melt some butter in a pan, add an equal amount of all-purpose flour, and cook it over medium heat while stirring constantly until it forms a smooth paste. Then, gradually whisk in your liquid (broth, stock, or drippings) until the gravy reaches the desired thickness. Make sure to cook the gravy for a few minutes after adding the liquid to eliminate any raw flour taste.
Cornstarch Slurry: Mix cornstarch with a small amount of cold water to create a slurry. Add this slurry to your hot gravy and stir well. The cornstarch will thicken the gravy as it heats up. Keep in mind that cornstarch can make the gravy slightly glossy.
Arrowroot: Similar to cornstarch, arrowroot is a starch that can be used to thicken gravy. Mix arrowroot with cold water to form a slurry and then stir it into the hot gravy. Arrowroot has a more transparent finish than cornstarch and can work well for clear sauces or gravies.
Beurre Manié: Beurre manié is a mixture of equal parts flour and softened butter, kneaded together to form a smooth paste. Add small amounts of this paste to the hot gravy while stirring until the desired thickness is achieved. Beurre manié gives a velvety finish to the gravy.
Reduction: Sometimes, you can thicken gravy simply by simmering it for a longer time to reduce the liquid and intensify the flavors. This works well if you don't want to use any additional thickeners.
When using any of these methods, make sure to bring the gravy to a simmer after adding the thickening agent and allow it to cook for a few minutes to ensure it reaches the desired thickness and any raw taste from the thickener is eliminated. Keep in mind that the gravy will continue to thicken as it cools, so it's better to slightly under-thicken it than make it too thick.