2 tablespoons butter
1 tablespoon olive oil
2 large leeks (white and pale green parts only), thinly sliced (about 2 c.)
1 large onion, chopped
Celery root (celeriac), peeled and cut into 1/2-inch cubes (about 5 1/2 c.)
Russet potatoes, cut into 1-inch pieces (about 12 oz.)
2 c. chopped celery stalks (including leaves)
1 1/2 t. minced fresh thyme
1 bay leaf
7 c. chicken broth (or 7c. water and 7 t. chicken base, which is what I used)
1/3 c. whipping cream
Salt, to taste
Freshly ground black pepper, to taste
Additional chopped fresh thyme (as a garnish)
Melt the butter with the oil in a large stock pot over medium heat. When sizzling subsides, add the leeks and onion, and sauté for about 10 minutes, stirring occasionally. Stir in the celery-root cubes, potato cubes, chopped celery, 1 1/2 t. thyme, and the bay leaf. Add broth, increase heat to high, and bring to boil. Reduce heat, cover, and simmer until vegetables are tender, about 40 minutes. Compost bay leaf (oops--I forgot to do this and puréed it together with everything else). Using immersion blender, carefully purée soup in pot. (Alternately, carefully purée in batches in a regular blender or food processor.) Stir cream into soup. Season to taste with salt and pepper. Ladle soup into bowls. Garnish with additional chopped thyme.
This is very, very good. It's smooth, rich (but not overly so), and has a beautiful celery flavor. The chopped thyme sprinkled on top complements the flavor of the bisque so well.
Happy birthday, Steve!