Palestine Soup with Sunchokes

From the garden

• 1½ lb sunchokes, scrubbed and roughly chopped
• 2 medium leeks, white and pale green parts, sliced and washed
• 4 sprigs fresh thyme
• 2 tbsp fresh chives, finely sliced

From the pantry

• 3 tbsp butter
• 1 bay leaf
• 5 cups vegetable stock
• ⅓ cup heavy cream · stirred in off the boil, at the very end
• 1 lemon · half for the holding water, half squeezed into the finished pot
• 4 slices crusty bread (optional) · for serving
• salt · to taste
• black pepper

1. Scrub the tubers hard under running water with a stiff brush, working into the knobs where soil hides, and trim any dark or shrivelled ends. Peeling is optional and the thin skin is good eating, so chop them into rough half-inch pieces and drop them straight into a bowl of water squeezed with half the lemon, which stops the cut faces browning.
2. Melt the butter in a heavy pot over medium-low heat and sweat the leeks with a pinch of salt for about 8 minutes, until soft and sweet but still pale. Colour on the leeks muddies the finished soup.
3. Drain the sunchokes, add them with the thyme sprigs and the bay leaf, and turn everything in the butter for 3 minutes until the pieces are glossy and smell faintly of artichoke.
4. Pour in the stock, bring to a gentle boil, then cover and simmer 30 minutes, until a knife slides into the largest piece with no resistance at all. Long, slow cooking is what softens the inulin that makes sunchokes hard on some stomachs, so keep the full half hour rather than pulling the pot early.
5. Lift out the bay leaf and the bare thyme stems, then blend until completely smooth, in batches with the lid vented if using an upright blender. Return the puree to low heat, stir in the cream and the juice of the remaining lemon half, and season generously with salt and pepper.
6. Ladle into warm bowls, scatter the chives over the surface, and serve with crusty bread.