I pulled three celeriac roots which, after hacking off all the unusable bits, weighed 500g. I've added a pint of veg stock to that, plus an onion, plus as many fennel fronds as I could cut from the big stem I brought home. I should have used the bulbous fennel stem but there wasn't one(!) so this soup is going to be more celeriac that fennel-flavoured. After I've blended it with my favourite kitchen accessory, my hand blender, I quite often have to add more water, but as celeriac is such a watery-type of veg it may be fine this time..