This light soup makes a hero of tender leeks, while a generous
amount of parsley brings a burst of grassy freshness. To take it
gluten-free, add a swirl of crème fraîche in place of the
70 gmbutter, diced3leeks, rinsed well, thinly sliced2celery stalks, thinly sliced2garlic cloves, finely chopped1floury potato (such as sebago, about 250gm), coarsely grated2thyme sprigs1fresh bay leaf1 litre(4 cups) chicken or vegetable stock150 mlpouring cream1 cup(firmly packed) flat-leaf parsley, plus extra coarsely chopped, to serve1 cup(firmly packed) baby spinach leavesButtery croûtons120 gmbutter, diced2thin slices day-old sourdough bread, crusts removed, cut into cubesJuiceof ½ lemon and finely grated rind of 1 lemon
Melt butter in a large saucepan over medium-high heat, add leek, celery and garlic and stir occasionally until tender but not coloured (4-5 minutes). Stir in potato, thyme and bay leaf, season to taste, then add stock and cream. Bring to a simmer, half-cover with a lid and continue to simmer until well flavoured and potato is tender (5-10 minutes). Discard thyme and bay leaf. Add parsley and spinach and stir until wilted, then purée with a hand-held blender and adjust seasoning to taste.
Meanwhile, for buttery croûtons, melt butter in a frying pan over medium-high heat. Add bread and fry, stirring occasionally, until golden brown (4-5 minutes). Strain butter through a heatproof sieve into a metal bowl and stir in lemon juice. Toss croûtons with lemon rind in a separate bowl.
To serve, ladle soup into bowls, scatter with croûtons, drizzle with a little hot butter and scatter with chopped parsley.