Warm broth over medium-low heat in a small sauce pan.
While the broth is warming, place a wide bottomed pan (a roasting pan works great) over medium-low heat and melt the butter into the pan drippings. Sprinkle in the flour and whisk continuously. Keep whisking until all the flour and fats are fully combined (usually about 5-7 minutes).
Increase heat to medium-high and slowly add vermouth while whisking continuously (Pro Tip: the fat and flour will want to clump as they combine and when added, the vermouth will bubble and quickly disappear. This is all to be expected, just keep whisking!)
Slowly add the warm broth and... keep whisking. Keeping adding broth and whisking until the broth is fully incorporated and the gravy is smooth. This should take about 5-7 minutes.
Add the soy sauce and Worcestershire and keep on whisking.
Add the herbs, salt, and pepper to your taste. And keep whisking.
Once you have the gravy seasoned exactly to your liking, remove the rosemary sprig and serve immediately before it cools.
Written by Lily Scott from Lily's Ladle.