6 tbsp. olive oil
6 cups chopped fresh fennel (bulbs only) Reserve some fronds for garnish
4 cups chopped leeks (whites and pale green only) soaked in abundant cold water to remove grit
6 cups vegetable broth
3 tbsp. fresh tarragon leaves
3 cups fresh spinach leaves
Special equipment if available: Vertical hand held blender
Heat oil in a large pot over medium heat. Add the leeks and fennel and a splash of broth, cover and sweat until softened but not browned, stirring occasionally. Season with salt and pepper and add the tarragon and broth.
If using a vertical blender, proceed as follows:
Add spinach all at one time by plunging into the soup and stirring just until the spinach is wilted. Puree until smooth with vertical blender and check seasoning, adjust if necessary.
If using a regular blender, proceed as follows:
Cool the soup for a couple hours. Quickly blanch spinach in a pot of boiling water. Immediately remove to a bowl of ice water to chill. Squeeze out excess moisture and add to chilled soup and transfer to a blender in small batches and puree until smooth. Check for seasoning and adjust if necessary.