• 4 tablespoons unsalted butter
• 1 large or 2 medium onions, diced
• 2 large bulbs celery root, peeled and cut into 1-inch cubes, covered with water acidulated with lemon juice
• 1 large russet potato, peeled and cubed
• 5 to 6 cups Chicken Stock
• 2 small bulbs fennel, trimmed and sliced
• Salt and freshly ground pepper
• Pinch (or to taste) freshly grated nutmeg

Melt the butter in a medium saucepan over medium heat. Add the onion and cook until translucent. Drain the celery root and add it and the potato to the onions. Pour in enough chicken stock to cover. Heat to boiling, then reduce the heat and simmer until the celery root is very tender. Add the fennel and simmer 5 minutes more.

Puree the soup in a blender or processor and thin if necessary with hot stock. Season to taste with salt, pepper, and nutmeg.