From “How to Cook Everything Vegetarian”
3 Tbsp butter or olive oil
1 small onion, sliced
1 pound celery, chopped
1 potato, peeled and roughly chopped
Salt and pepper
5 cups vegetable stock or water
2 tsp sugar, or to taste (optional)
½ cup cream or sour cream (optional)
¼ cup chopped celery leaves for garnish
Put the butter or oil in a large, deep saucepan or casserole over
medium heat. When the butter melts or the oil is hot, add the
vegetables. Season with salt and pepper and cook, stirring occasionally,
for about 15 minutes, until the celery softens a bit. Add the stock and
cook until the vegetables are very tender, 15 to 20 minutes.
Use an immersion blender to puree the soup in the pan, or cool the
mixture slightly, and food process it in batches. Adjust the seasoning.
Stir in the cream, garnish, and serve hot or chilled.