Make soup base: In a large pot heat the oil, add the onion, garlic, leek and celery and cook for 2-3 minutes until softened, stirring frequently.
Add zucchinis and potatoes: Add the zucchinis, potatoes, tarragon, stock (approx. ⅔), stir, cover and bring to the boil.
Cook soup: Lower the heat and simmer for about 20 minutes stirring occasionally.
Puree soup: Remove from the heat and puree. Top up with more stock if needed, adjust the seasoning and serve.
I recommend using medium size zucchinis as very large ones can sometimes be too bland.
Potatoes: Use all-rounders such as russets or Yukon Gold, Maris Piper or King Edward potatoes.
Herbs: My choice of herb was tarragon, which has a sweetish, slightly aniseed flavour, really lifting the bland zucchini. Zucchinis, however, pair well with virtually all herbs so use your favourite. You could also omit the herbs altogether.
Consistency: You may need a little less or more stock than the recommended amount depending on personal preference so add a little less to start with.
Serving: Best served hot. Scatter over lightly toasted seeds or croutons for crunch. For a non-vegan option serve with a knob of butter or sprinkle of cheese such as parmesan or another strong cheese.
Keep refrigerated for up to 3 days.
Freeze individual portions in airtight containers for up to 3 months.