Finely chop the onion and garlic.
Heat the oil in a saucepan and gently sauté the onion and garlic, for about 8 minutes.
Meanwhile, peel and dice the parsnips and beetroots. Add these to the pan, together with the oregano and tomato purée. Stir for a minute, then add the water and stock pot.
Bring to the boil, turn down the heat and simmer under a lid for about 25 minutes, until tender.
Turn off the heat, add the herbs then whiz with a hand-held blender or in a liquidiser until you get a smooth, creamy soup. Add some more stock if it’s too thick.