Roast the Turkey
Cut a piece of Aluminum Foil just to loosely cover breast and cavity of turkey. Do not cover the entire turkey. Place roasting pan in the oven rack and roast for about 3 hours. There is no need to open oven or baste turkey during this time. Take foil off the turkey after 3 hours of roasting and leave the turkey to roast for an additional hour. Using a meat thermometer, check to see if your turkey reach 160 degrees F. If the breast and thigh reached 160 degrees, then your turkey is done. Take Turkey out and let in rest at room temperature for 30 minutes completely covered with aluminum foil (resting the turkey after cooking is a very important step if you want to get that juicy flavor.) While your turkey is resting, carefully, lift the turkey with the rack and pour the juices from the pan in a bowl using a strainer. You can throw the carrots, celery, and onions away. Start making your gravy.
Make Your Gravy
In a cooking pot, over medium heat, melt the butter and add onions to it. Cook onions for about 6-8 minutes till they become soft and translucent. Add the flour to the onions and mix with spoon to ensure all the onions are evenly covered with flour. Add all the herbs and turkey juices, stirring with spoon till you get a thickened sauce. Gradually add the chicken broth while stirring at medium low heat till you reach desired thickness of gravy. Add cream at the end. Sprinkle salt and pepper as desired.