Heat the oil or butter in a large stock pot.
Add the onions and cook gently for 10 minutes until soft.
Add the garlic and celery and cook for 1–2 minutes.
Add all the vegetables to the pot.
Add the stock pots, thyme, bay leaves and boiling water.
Bring to the boil, then reduce to a simmer.
Cook for 35–40 minutes until all vegetables are completely soft.
Remove the bay leaves.
Blend until smooth.
Season well with salt, black pepper and white pepper.
Stir in the cream.
Adjust thickness with a splash of hot water if needed.