Vichyssoise — Classic Cold Leek and Potato Soup

Instructions

1. Melt the butter in a large saucepan over medium-low heat. Add the onion and leeks with a pinch of salt. Cook gently, stirring occasionally, for 15 minutes until completely softened but not coloured — this low-and-slow step is the foundation of the soup's sweetness.
2. Add the diced potatoes and stir to coat in the butter. Pour in the stock, bring to a boil, then reduce to a simmer. Cook for 20 minutes until the potatoes are completely tender.
3. Remove from heat and allow to cool slightly. Blend the soup in batches until absolutely smooth — use a high-powered blender for the silkiest result, blending each batch for 90 seconds.
4. Pass the blended soup through a fine-mesh sieve, pressing firmly with a ladle to extract every drop. This step, though optional, gives vichyssoise its characteristic velvet texture.
5. Stir in the crème fraîche. Season assertively with salt and white pepper — cold temperatures dull flavour, so the soup needs more seasoning than it seems.
6. Cool to room temperature, then refrigerate for at least 3 hours until well chilled (overnight is ideal).
7. Serve in chilled bowls, finishing each with a swirl of crème fraîche, snipped chives and a drop of truffle oil if using.

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