Serves 4

When choosing avocados, avoid any with blemishes or bruises. Ripe ones will yield under gentle pressure and the skins of some varieties, such as Hass avocados, turn black or dark green. To speed up ripening, place the avocado with an apple in a brown paper bag and leave in a warm place.

2 tbsp olive oil, plus extra for frying
1 onion, peeled and finely chopped
Sea salt and freshly ground black pepper
3 slices of Parma ham
Splash of dry white wine or vermouth
1 medium potato, peeled and chopped
1 bouquet garni (a sprig of thyme, bay leaf and a few parsley stalks tied together)
750ml chicken or vegetable stock
250g frozen peas
1 large ripe avocado
Juice of half a lemon

1 Heat the oil in a large pan and add the onions and some seasoning. Give it a stir, then cover and reduce the heat to low. Sweat for 5-7 minutes until the onions are soft but not coloured. Meanwhile, fry the Parma ham on both sides in a little extra oil until golden and crisp. Remove with a slotted spoon and drain on kitchen paper.

2 Remove the lid from the onion pan, turn up the heat slightly and add a splash of white wine or vermouth. Cook until the wine has bubbled down to a syrupy glaze. Tip in the potato and bouquet garni and stir well. Pour in the stock and bring to the boil. Season again and leave to simmer for another 10 minutes until the potato is soft.

3 Tip in the peas, return the soup to the boil and cook until the peas are tender. Fish out the bouquet garni and discard. Halve the avocado, remove the stone and scoop out the flesh into a blender.

4 Ladle in half the soup and blend to a smooth purée. If you want it really smooth, push the purée through a fine sieve into a clean pan. Liquidise the remaining soup and add to the rest. Add salt, pepper and lemon juice to taste, then reheat gently. Ladle into warm bowls, then break the crispy Parma ham into pieces and sprinkle over to serve.

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