In a medium saucepan, heat drippings, chicken broth, butter, garlic powder, and onion powder until melted and hot but not yet boiling. Remove 1/3 cup of the hot liquid into a smaller bowl and whisk in 1 teaspoon arrowroot powder until dissolved into a slurry, then pour back into sauce pan. Repeat one to two more times with arrowroot powder slurry. Bring to boil, then turn down heat to a simmer and let sauce reduce, until gravy thickens to desired consistency, about 15-20 minutes, whisking frequently. If the gravy still feels too thin, make the arrowroot powder slurry, 1 teaspoon at a time, until desired thickness. Be careful not to over thicken the gravy, lest it become too gooey. Season with salt and pepper to taste, if needed. Remove from heat and whisk in heavy cream, if desired, for a thicker, richer gravy. Serve immediately.