Related: Cauliflower Mashers recipe
1. Place broth, water, celery root, dried mushrooms, shallots and garlic into large pot and bring to a boil over high heat.
2. Reduce heat and simmer for 20 minutes.
3. Turn off heat and steep for 1 hour.
4. Strain into a medium mixing bowl and press mushroom and celery root mixture with a spoon to extract all the juices and thicken the gravy.
5. Season with salt, pepper and rosemary to taste.