This soup is beautiful, warm and elegant, with wonderful earthy base-note flavours. It does contain very little water and an unusual amount of olive oil, but don't be put off by that. One taste and you'll know it's good for you. Serve the soup simply on its own; it needs no further accompaniment.
180g/6oz dried porcini
300ml/1/2 pint warm water
120ml/4fl oz good extra-virgin olive oil
3 shallots, peeled and finely chopped
6 sprigs rosemary, leaves only
3 garlic cloves, peeled and finely chopped
1 small dried red chilli
1kg/2lb Roseval potatoes
Sea salt and freshly ground black pepper
60g/21/2oz Parmesan, grated
The juice of half a lemon
A bunch of curly parsley, leaves only, very finely chopped
Start by placing the porcini in a bowl. Pour over the warm water and leave for 10 minutes or so for the porcini to soften and for the water to be infused with their lovely, musty flavour.
Place a large heavy-based pan over a low heat, add a tablespoon of the olive oil and when just warm, add the shallots. Cook over a low heat for five minutes to soften.
Chop the rosemary finely and add to the shallots along with the garlic. Crumble over the chilli and stir well to combine.
Slice the potatoes into ¼-inch rounds (do not bother to peel, as the skin is delicious). Strain the porcini, reserving the infused water. Chop fairly roughly and add to the pan with the potatoes.
Add the rest of the olive oil, a good pinch of sea salt and a little freshly ground black pepper, stir to coat and cook gently for 10 minutes, stirring every now and then.
Pour in the reserved water and continue to cook until the potatoes are tender and beginning to fall apart. Add the Parmesan and the lemon juice. Sprinkle over the chopped parsley, taste one final time and add what you feel is necessary - perhaps a little more pepper and a pinch or two of salt. Ladle into warm bowls and serve.
Skye Gyngell is head chef at Petersham Nurseries, Church Lane, Richmond, Surrey, tel: 020 8605 3627