Food & Drink: Nutty fruit of a well-hung tree: So smooth it used to be known as 'midshipman's butter', the avocado makes delicious salads, soups and sandwiches

I have never thought of the avocado as a particularly suggestive fruit, but the Aztecs did: our word avocado derives from their ahuacatl, which meant 'testicle tree'. I suppose those plump green fruit dangling down among thick, glossy leaves made the tree seem spectacularly well endowed.

Be that as it may, one of the quirks of the avocado is that it will not ripen on the tree. Nature ensures that the avocado drops to the ground when it is mature in the sense that it has reached full size and is ready to ripen, but before it begins to soften. Commercial growers have to time their harvest carefully. If they pick too soon, the fruit will be too immature to ripen properly; too late, and the crop may become too bruised to sell.

Plucked from the tree at just the right moment, avocados will take between one and two weeks to ripen at room temperature. Their thick, waxy skin ensures that they will not dry out, unlike so many fruit. At home, the final ripening process should present no problem. Avocados need no more than a warm, airy place - the ideal temperature is 60F/15.5C but a little warmer will not hurt. They should not be refrigerated before they are ready to eat.

Avocados originated in Mexico, but long before the Spanish reached the New World they were being cultivated as far south as central Peru. They belong to the laurel family, and botanically fall into three groups. The West Indian avocado, famed for its size if not its savour; the Guatemalan, with medium-sized fruits encased in a gritty, granular skin; and the Mexican, small-fruited with anise- perfumed leaves that are sometimes used as a flavouring.

Many of the best varieties of avocado are crosses between the main groups. Dark, pebbly- skinned Hass, for instance, is a Guatemalan-Mexican hybrid and so, too, is one of the other most common varieties, Fuerte. Hass has a particularly good, nutty flavour and is as smooth as butter (one of our old names for it was 'midshipman's butter'). Both qualities are largely the result of the high oil content (depending on where the Hass is grown, it can contain up to 35 per cent oil), which unfortunately also means that it is loaded with calories.

Many of the West Indian varieties can grow almost as big as footballs but contain little oil (as low as 2 per cent). The consequence is plenty of watery, dull-tasting flesh, which needs a generous hand with spices, herbs and other seasonings to make it worth eating.

Avocado and grapefruit salad

An inherited favourite from my mother, and what I shall be having for supper when I finish this article. You will need to choose an avocado that is only just ripe; firm enough to slice neatly.

Serves 3-4

Ingredients: 1 grapefruit, pink for preference

1 just-ripe avocado

chopped tarragon, chervil or parsley

For the dressing: 1tbs white wine vinegar or tarragon vinegar

a hint of Dijon mustard

a pinch of sugar

5tbs olive oil

salt and pepper

Preparation: Make the dressing in the usual way. Peel the grapefruit, removing as much pith as possible, then divide into segments. Pull off the papery skins as well as you can. Slice the avocado and turn in some of the dressing.

Arrange avocado and grapefruit segments on a plate, drizzle over a little more of the dressing (you will not need it all), and scatter with herbs.

Avocado and yoghurt soup

A perfect, simple summer soup, full of verve but refreshing and satisfying, and an elegant pale green.

Serves 4-6

Ingredients: 2 ripe avocados

1/2 pint (290ml) thick Greek

yoghurt

1/2 pint (290ml) water

lemon juice

2 cloves garlic, crushed

2tbs chopped fresh mint

2 firm tomatoes, deseeded and diced

salt and pepper

Preparation: Halve the avocados and remove the stones. Rub the cut surface of one half with lemon juice and set aside. Scoop the flesh of the rest into a blender and quickly add the yoghurt, a dash of lemon juice, the garlic and the mint. Whiz to a smooth paste and gradually mix in the water. Season to taste. Cover with clingfilm and chill for an hour. (If you want to keep it for more than an hour, get the clingfilm right down on to the surface of the soup to delay oxidisation. It will still be edible 24 hours later, and the light-brown surface can be stirred into the soup with no harm done.)

Shortly before serving, dice the remaining avocado and mix into the soup. Serve in small bowls, garnished with tomato.

Avocado and smoked bacon ciabatta

This is a recipe stolen from London sandwich bars. I adore the taste of salty bacon against the smooth richness of avocado. Adding basil and generous seasoning, and wrapping it in chewy ciabatta bread puts it among my favourite sandwiches. If you want to get really fancy, use home-made mayonnaise sharpened with lemon juice and lifted with finely grated lemon zest.

Serves 3-4

Ingredients: 1 ciabatta, split in half horizontally

4 rashers smoked back bacon, grilled until crisp and broken up

1 ripe avocado

4tbs mayonnaise

6 basil leaves, roughly chopped

2 ripe tomatoes, sliced

a generous handful of frisee lettuce

lemon juice

salt, pepper and cayenne papper

Preparation: Mash the avocado roughly with 2tbs of the mayonnaise. Stir in the bacon and basil leaves. Taste and season with salt and cayenne pepper and a little extra lemon juice if needed. Spread thickly over the lower half of the ciabatta. Lay tomatoes on top, season with salt and pepper, then add the frisee. Spread the upper half of the ciabatta with the remaining mayonnaise and clamp it down firmly on top. Eat straight away, cut into large wedges.

Sweet avocado fritters

This recipe may sound far from enticing, but I promise you, the result is astonishingly good. The avocado itself is just heated through, but not so cooked that it goes slimy, and it marries very well with the rum.

Serves 8

Ingredients: 2 ripe avocados

2oz (55g) castor sugar

3tbs rum

a little icing sugar

wedges of lime to serve

oil for deep frying

For the batter: 3oz (85g) flour, sifted

pinch of salt

1tbs rum

2 eggs, separated

1tbs oil

Preparation: Peel and stone the avocados and slice thickly across the width to form crescents. Mix with the castor sugar and 3tbs of rum. To make the batter, sift the flour with the salt and make a well in the centre. Add the rum and egg yolks and gradually mix in enough water to give a smooth batter with the consistency of thickish single cream. Rest for half an hour. Just before using, whisk the egg whites until stiff. Add the oil to the batter and fold in the egg whites.

Heat the oil to about 195C/ 385F. Drain the avocado, and dip pieces into the batter, coating evenly. Fry until puffed and golden. Drain briefly on kitchen paper, dust with icing sugar and eat quickly with a squeeze of lime juice before the butter turns soggy.