Four years ago, my downstairs neighbour was going away for a week, and she came by with two eggs and a small brown paper bag full of produce, and that was the first time I saw celery root. I couldn't fathom eating such a primitive ungainly ur-vegetable, but my ever-capable German flatmate Marion – in Berlin for a few months between stints at a women's-rights nonprofit in Pakistan – knew exactly what to do. She peeled, she trimmed, she sliced, breaded and sauteed, and there we were dining on satisfyingly crisp rounds of celery root, flavoured with a quick squeeze of lemon juice while the cat, Paul, purred on the red floorboards.

Though I've eyed it in the shops since then, I never got around to buying celery root until Saturday. I had been round at Joanna's the night before, and tasted a bit of the soup she had simmering on the stove just before I left to try and guess what it needed. That spoonful induced a craving for that clear, uncomplicated taste of celery root, and the next day at the Bio Company I was up on my tiptoes trying to find one which was heavy without seeming woody. Once home, David goggled at the alien growths, but then dunked it into the sink for a good scrub, and we were off.

Celery root cream soup (based roughly on an Epicurious recipe)

• 1/4 C butter
• 2 small onions, peeled and roughly chopped
• 1/2 tsp dried thyme
• 1/2 tsp dried rosemary
• 3 celery ribs, chopped into chunks
• 2 lb celery root, peeled and chopped into chunks
• 10 new potatoes, roughly chopped (I didn't peel mine and didn't regret it)
• 5 C stock
• 1/8 c dry white wine
• 1/3 C whipping cream
• coarse black pepper
• salt

Melt the butter in a large heavy-bottomed soup pan, then add the onions and herbs and saute till translucent, then add the chopped celery ribs and saute for five minutes. Add the celery root, potatoes and stock, and cover and simmer for 45 minutes. Puree, add whipping cream, and season to taste with black pepper and salt.