Instructions

1. Preheat the oven to 350°F. Scrub the celery root. In a small bowl, stir together the salt, ash, and water to make a paste that holds together when you squeeze it with your hand (the amount of water will depend on how dense the ash is).
2. Spread the paste all over the celery root, pressing down so that it adheres, and place the celery root in an ovenproof dish. Bake until you can easily insert a small knife, about 2 hours.
3. Just before the celery root comes out of the oven, melt the butter in a small pan over low heat, then stir in the parsley. Set aside.
4. Remove the celery root from the oven and crack the crust open with a meat mallet. With a small paring knife, peel the charred celery root, then slice it lengthwise and arrange on a platter.
5. Drizzle the parsleyed butter over the top and serve immediately.