Replacing ingredients in any recipe can change the resulting product. A recipe is a chemical formula with all the elements in certain proportions put together with a specific method to produce your cookies in the way you are used to experiencing them. Replacing butter in your cookie recipe, especially with a low-fat or nonfat Greek yogurt, can change the moistness and shelf life of your favorite cookie. However, Greek yogurt can also add creaminess and tenderness to your recipe, cut the fat content and provide extra calcium and protein.
Replace one-half the butter in your cookie recipe with half as much full-fat Greek yogurt. For example, if the cookie recipe calls for 1 cup of butter, you can use 1/2 cup of butter and 1/4 cup of Greek yogurt. Experiment substituting more yogurt for butter to determine if you still like the taste and texture of your cookie with little to no butter.
Stir 1 tbsp. of cornstarch in your yogurt if you are substituting nonfat Greek yogurt in your cookie recipe. This will keep the yogurt a smooth consistency while baking.
Replace oil or shortening in your cookie recipe if your recipe calls for these ingredients rather than butter. Replace one-half the oil or shortening in the recipe with three-quarters the amount of Greek yogurt. For instance, if your cookie recipe calls for 1 cup of oil, use only 1/2 cup oil and about 1/3 cup of Greek yogurt.