Reusing the leftover potato water is also a great way to ensure you obtain beneficial nutrients, such as vitamin C and potassium, which are often lost during boiling.
The first step is to determine how much potato water you will need, as the water will essentially replace the flour or cornstarch and some of the liquid in a regular gravy recipe.
Once you have the correct amount of water for the gravy, simply add the drippings from your roast or turkey along with your preferred broth, salt, and pepper.
Simmer the mixture until it thickens. If you're not cooking meat, you can also use beef or chicken bouillon toasted in butter to replace the drippings.