Basic turkey gravy is made from butter, mirepoix, poultry stock, roux, herbs and spices. Gravy consistency, taste and flavors differ from cooking techniques, recipes and more or less ingredients.
Most of the calories in the gravy are from the Roux a flour and butter/ fat combination. To make a less calories gravy change the roux from regular white baking flour and butter / fat with a less calories flour that can be mixed with plain water like tapioca flour, arrowroot. Here is the calories difference: 100 grams of white flour has 364 calories, arrowroot is 64 only calories per same amount or tapioca flour with 115 /100g . Do not use cornstarch since 100g of it will add even extra calories then white flour more precisely 381 calories. Rice flower has about 325 calories per same amount which isn’t a big difference.
Controlling the butter amount also cut into the calories of the dish, (100g of butter has 717 calories) you can replace butter with fat drippings from the pan where turkey was cooked for more flavor but wont cut the calories and may even increase it. The key to a less calories gravy is the water replacing butter for a total of zero added calories.
Fallowing is the process of making the gravy . In pot at low temperature add a small amount of butter, add diced onion, diced celery and diced carrots ( mirepoix) and cook to soften. Add poultry stock (optional you can add a bay leaf at this time for more aromatic flavor) and let simmer for 10 minutes to extract flavor form vegetables. On the side prepare arrowroot by following package instruction for thickening amount. Add to the stock. Once consistency is achieved remove and strain everything to remove all vegetables. To achieve same look of traditional gravy add a small amount of cream milk (cloud the gravy) and small amount of butter for added shine. Adjust taste if needed. This method can followed for other similar texture gravies like beef with the difference that poultry stock will be replace with beef stock