Celery root is a great winter vegetable. Here, it's combined with interesting ingredients to make a warming winter soup. An immersion blender is perfect when dealing with hot liquids–and it cuts the clean up time down so there's more time to enjoy this delectable dish.
The equipment recommendations expressed in the Kitchen Corner department are those solely of Melissa Clark.
Melt the butter in a large pot over medium heat. Add the leeks and celery; cook, stirring occasionally, until softened, about 5 to 10 minutes. Reduce the heat, to prevent the vegetables from browning.
While the leeks are cooking, start cleaning and chopping the celery root and potatoes. Once the leeks are softened and translucent, add the chopped garlic and a pinch of salt.
Finish cleaning the celery root and potatoes. Cut the vegetables into large, equally sized chunks.
Add the cleaned celery root and potato chunks, and 10 cups of water to the pot, enough to cover the vegetables by 1 inch. Raise the heat to high. Tie the thyme and sage together and drop into the pot (reserve the extra sage leaves for the oil). Add freshly ground black pepper, to taste. Bring everything to a boil; reduce immediately to medium-low heat and simmer until all the vegetables are very tender, 20 to 30 minutes.
Remove the pot from the heat. Remove and discard the herb bunch. Using an immersion blender, puree the soup until smooth. Add water to adjust the consistency, if necessary.
Taste and adjust the seasoning, if necessary. In a medium skillet, warm the oil over medium heat. Add the sage leaves and cook until they turn deep green, 10 to 15 seconds. Remove from the heat.
Ladle the soup into warm bowls. Drizzle sage oil over the soup and nestle a few of the sage leaves on top. Serve with optional wedges of lemon. Serve immediately