Step 1Trim the tops and ends of the fennel bulbs. Save a few of the green fronds and chop them for garnish; set aside. Thinly slice the bulbs. You should have about 4 cups sliced fennel.
Step 2Saute the sliced fennel, chopped onion and sliced carrots in the olive oil in a large saucepan until tender, about 20 minutes.
Step 3Add the chicken broth and bring to a simmer. Cover and simmer about 20 to 25 minutes, until the vegetables are very tender.
Step 4Puree with an immersion blender right in the saucepan, or in a food processor in one or two batches, transferring each batch to a clean saucepan or warm tureen.
Step 5Spoon into serving bowls and sprinkle with chopped fennel fronds and cracked black pepper.