Bring the broth to a boil over medium-high heat. Allow it to simmer until it has reduced by half. Stir it occasionally to prevent it from scorching and reduce heat if needed.
Remove from the heat and whisk in ¼ tsp of xanthan gum. Allow it to sit for 2-3 minutes then add an additional ¼ tsp if the gravy is still too thin. Be careful not to add too much xanthan gum as it can cause a slimy, gel-like texture. If you do find that you have added too much, you can fix it by simply adding additional broth until you reach the desired consistency.