2 Tablespoons butter
1 1/2 Pounds (12 to 15 large stalks) celery, sliced 1/2 inch thick crosswise (about 6 cups), leaves reserved for garnish
1 medium onion, coarsely chopped
1 baking potato, (8 to 10 ounces),peeled and cut in 1/2 inch cubes
1 to 2 Tablespoons fresh lemon juice
- Heat butter in a large (4-quart) saucepan over medium heat. Add celery, onion, and potato; season with salt. Cook, stirring occasionally, until vegetables begin to soften, 8 to 10 minutes.
- Add 6 cups water to saucepan; bring to a boil.
- Reduce heat to medium, and simmer until vegetables are very tender, about 20 minutes.
- Working in batches, purée soup until smooth. (To prevent splattering, fill blender only halfway, and allow the heat to escape: Remove cap from hole in lid; cover lid with a dish towel, holding down firmly while blending.) Return soup to pan; stir in lemon juice, and season with salt.
- Serve, garnished with celery leaves.