Separate the broccoli into stems and florets. Trim away the tough outer part of the stems. Select about 1 cup of the nicest looking florets for garnish. Coarsely chop the remaining stems and florets.

Heat oil in a soup pot over medium heat. Add the onions, celery, leeks and chopped broccoli. SAute, strring frequently, until the onions are softened and translucent, about 5 minutes. reserve the liquidAdd the flour and stir well to combine. Cook, stirring frequently, for 4 minutes. Gradually add the broth to the pot, whisking to work out an lumps in the flour. Bring soup to a simmer and cook for 45 minutes. Stir frequently and skim as needed.

Remove the pot from the heat and let the soup cool for at least 10 minutes before pureeing with an immersion blender or blender. Strain the soup through a sieve and reserve the liquid. Add the solids to the blender jar or food processor; do not overfill. Add a little of the liquid, and puree until smooth. Add more liquid if necessary to help puree the solids. Transfer the puree to a clean pot. Continue ato puree until all the solids are blened with the liquid. Adjust the consistency by adding the remaining reserved liquid. The soup can be cooled and stored up to 2 days in your refrigerator or 1 month frozen.

When ready to serve, steam or boil the reserved broccoli florets until just tender. Return the soup to a simmer over low heat and add the heated cream. Season to taste with salt, pepper and fresh squeezed lemon juice.

Serve and garnish with florets.