Jerusalem artichoke soup (with a digression on celeriac)

Leg two of the jerusalem artichoke journey - I made soup. It's a classic - it's how I ate these vegetables the first time and I wanted to see whether I could make something as good as what I had. This soup should be earthy, creamy, nutty and infused with that unmistakeable aroma that only these little tubers have. It is the perfect winter soup - tasting much richer than it actually is and pressing all sorts of comfort food buttons. But I don't like my soups too rich, so I don't add cream and only use a little butter.

Butter is essential - even a little bit adds a depth and moreishness that oil can't bring to the dish. The other night we ate a celeriac and potato mash with some lamb - no cream, no seasoning, just two medium potatoes, a small head of celeriac about the size of my fist. Peel and boil the potatoes for 15-20 minutes depending on your potato type; in a separate pan boil the celeriac, peeled and cut into chunks, for a good ten minutes until tender enough to mash. Mix the potatoes and celeriac together and add a large knob of butter (we used about 10g - or was it less? - for two people) before mashing. This would go wonderfully with some game or a good sausage too.

Here is the soup recipe, with some guidance from Nigel Slater.

Serves 4
a knob of butter
light olive oil
1 medium onion
1 medium leek
500g jerusalem artichokes (unpeeled weight)
2 bay leaves
about 1 litre light stock or water
a small bunch of parsley to serve

(changes I made: I use much less butter and add a little oil instead. Nigel Slater uses 40g butter. He uses two large leeks and no onion in this recipe. I used what I had in the house!)

Melt the butter with the oil in a pan over a moderate heat. Wash, trim and slice the leeks finely and chop the onion finely, then sweat them in the oil and butter for about 20 minutes over a low-moderate heat until very soft. Be careful not to let them brown, just soften them without colouring. Peel the artichokes, dropping the peeled ones into a bowl of cold water to which the juice of half a lemon has been added. This stops them from discolouring whilst you peel the rest. Once they are done and the leek and onion is soft, chop the artichokes into chunks and add to the pan. cook for a few minutes before covering with your stock (I used Marigold bouillon powder at half the recommended concentration) and adding the two bay leaves. Bring to the boil, then let it bubble over a medium heat with the lid slightly ajar for about 25 minutes. After this time, let the soup cool a little before blending it in batches in a blender or food processor. If necessary, reheat to serve and add lots of chopped parsley just before serving.

Some people would add cream to the soup just after it has been blended. I think it's completely unnecessary because the soup is naturally so rich and moreish. This was simply beautiful and didn't cause too many gut troubles afterwards (some people say that peeling them helps with this).