Heat the vegetable oil in a large soup pan on a low heat
Add the onion, celery and garlic, cook for around 5 minutes, until soft
Add the water, carrot, potato, thyme, rosemary and vegetable stock and bring to the boil
Boil for 12 minutes, then add the broccoli
Boil for a further 5-8 minutes, until the vegetables are soft
Remove from the heat and use a stick blender to puree the mixture
Add the salt, and stir in. You can also add more water at this point if you want a thinner soup
Serve immediately, or allow to cool fully and store in the fridge in an airtight container for 2-3 days. Or in the freezer for up to 3 months