Cut enough 1-inch florets from broccoli to measure 2 cups. Cut rest of broccoli into 1-inch pieces. Cook florets and broccoli separately, in lightly salted water; until just tender. (Florets will be done first.) Immediately rinse in cold water to chill completely. Drain. Set florets aside until serving time.
In a large saucepan, saute leeks in butter until tender; about 3 - 4 minutes. Sprinkle in flour and cook for a minute or so, stirring with a whisk. Remove from heat and stir in chicken stock. Return to heat and simmer 5 minutes stirring occasionally.
Add broccoli pieces (not florets) to chicken stock and puree in an electric blender, in batches, until smooth.
Shortly before serving, blend in cream and cheese. Simmer gently until cheese melts. Add nutmeg, and salt and pepper to taste. Add reserved broccoli florets to heat through. Serve immediately.