This soup tastes slightly different every time depending on the strength of the herbs used. You can vary the herbs, but the stronger ones like thyme, rosemary, coriander and tarragon dominate and overwhelm the subtle fragrance of the soup. Open to interpretation is allows you to bias it towards what you like and what you have in the garden/fridge/cupboard today. . It may look strange, greenish, but is absolutely delicious. 
It lives in the fridge very well for a few days (i tested 4 days, no reason for concern at all). So you can prepared it ahead of time, and you can serve leftovers the next day without any loss of fragrance or taste (keep it well, tightly covered, though).
Blueprint configuration for 6-8:
- 1 small fennel bulb, roughly chopped,
- 1 leek, roughly chopped and washed,
- 1 medium onion, peeled and roughly chopped,
- a bunch of fresh kale. washed, divided (leaves chopped separately, stems sliced to cook in step (3),
- 1tbsp vegetable oil,
- 1tbsp flour,
- 1.5 litre vegetable stock,
- Salt and freshly ground black pepper,
- A handful of parsley, washed, thicker stalks removed and put to one side,
- A handful of chervil, washed, thicker stalks removed and put to one side,
- A handful of basil, washed, thicker stalks removed and put to one side,
- Approx 10g chives,
- A few mint leaves,
- crostini or choux pastry, creme fraiche, or goat cheese to serve with the soup.
- Gently cook the fennel, onion and leek in the vegetable oil in a covered pan for 4-5 minutes until soft, stirring every so often.
- Add the flour and stir well then gradually add the vegetable stock and season.
- Bring to the boil; add the thicker reserved herb stalks and simmer gently for 20 minutes.
- Add the rest of the greens and simmer for 2 more minutes only.
- Blend until smooth in a liquidizer then strain through a medium strainer, as a fine- meshed sieve will not allow some of the bits of herbs through. We took the thick remnants from the strainer into a narrow tall dish and treated it with a hand-held blender (spinning butterfly steed blade style) – got most of it mashed completely – and the soup was pleasantly thicker.
- To keep its green colour, you may need to cool the soup down as quickly as possible; it depends on the types of greens you have. it you feel you want to, put the bowl of strained soup over another bowl of iced water.
- Re-season if necessary and serve from the fridge.
- If you feel like it, garnish with finely chopped herbs, cream or crème fraîche or even fresh goat’s cheese.
I serve it with small choux pastry balls and/or with crostini.