In a small saucepan, heat the butter over medium heat. Cook until fully melted, then add in the salt, pepper, sage, rosemary and garlic. Let cook 2 minutes, then whisk in the chicken broth. Bring to a boil and cook for 5 minutes, then lower to a simmer.
In a small glass or bowl, mix the arrowroot or cornstarch with a few drops of water, whisk together and pour into the simmering seasoned broth. Whisk well and let cook for 3-5 minutes until thickened. Remove from the heat and pour into a gravy bowl.