Thoroughly wash your leeks by chopping and then filling a large bowl or salad spinner with the leeks, keep submerged in water until all the dirt is removed, then rinse thoroughly.
Wash and chop your celery stalks and peel, rinse and cube your potatoes.
Heat the olive oil over medium high heat and add the leeks, cook approx 10 mins being careful not to brown them, add in the celery and cook 2-3 mins before adding in your stock and potatoes. Add in the bay leaf and thyme bunch and 1 tsp salt and pepper and chili flakes and simmer 20 mins until the potatoes are fork tender.
When the potatoes are tender, fish out the thyme bunch and remove the bay leaf, use an immersion blender or transfer in batches to a standing blender to puree.
Return the soup to the pot and add in the cashew cream and finish with the lemon juice. Add in the remaining teaspoon of salt or more to taste. Garnish with a drizzle of good olive oil and serve with crusty bread to dip.