- Knob of butter
- 1½ tbsp olive oil
- 1 large onion, chopped
- 2 garlic cloves, crushed
- 2 leeks, thinly sliced
- 2 large, floury potatoes, such as King Edward, cut into chunks
- 1 litre chicken or vegetable stock
- 200g watercress, plus a few sprigs to garnish
- Large handful fresh parsley leaves
- 70g chorizo, roughly chopped
- Heat the butter and 1 tbsp of the olive oil in a large casserole over a medium-low heat. Add the onion, garlic and leek, season with salt and pepper, then sweat, stirring occasionally, for 10 minutes.
- Add the potato and cook for 5 minutes until it has softened slightly. Pour over the stock, bring to the boil and simmer for 10 minutes until tender. Add the watercress right at the end of cooking, stirring, until just wilted (about 1 minute). Do not overcook at this stage, or the watercress will lose its lovely colour.
- Leave to cool, then pour into a food processor (or use a stick blender), add the parsley and whizz until smooth. Pass through a sieve into a clean pan, using a wooden spoon to squeeze as much through as possible. Check the seasoning. At this stage, you can freeze the soup in a freezer bag or plastic box.
- Defrost the soup completely. Heat the remaining olive oil in a frying pan over a medium-high heat. Add the chorizo pieces and fry until they are crisp and are beginning to release some oil. Set aside.
- Meanwhile, warm through the soup, checking the seasoning, then spoon into warm bowls, and season with black pepper. Serve the crisp chorizo and its oil in a bowl on the side, then spoon over the soup. Enjoy with plenty of crusty bread and butter.
- Put freezer bags of soup inside plastic boxes to freeze as blocks – this makes for easy stacking. Be careful not to overfill.