Don't Sweat the Aubergine

with the pestle until it turns to a creamy pulp. Or grind it on a chopping board with the blade of a heavy knife. Then add the egg, but not the mustard, and proceed as above.
    You may prefer to save the tasting of such a powerful concoction until you find yourself on a sun-drenched terrace in Provence. Use only the garlic you want – but you probably shouldn’t give the name aioli to the garlic-lite version.
    For a tartare sauce, to accompany fish and chips, add to the mayonnaise a teaspoon each of chopped gherkins, capers and shallots.
    Rouille is a fiery mayonnaise with harissa ( see here and here ).
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WHY YOU DO IT
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    1 • Don’t start cold . Mayonnaise is an emulsion, in which droplets of oil are dispersed – thanks to your turning or whisking – in the liquid of the egg yolk, and in the vinegar or lemon juice. The emulsifiers in the yolks need waking up – they’re sluggish when cold, and when brought into contact with other cold ingredients. However, I usually find that I get away with using mustard from the fridge. I bring the egg to room temperature in lukewarm water.
    2 • What oil? I use 1/3 extra virgin olive oil, and 2/3 sunflower oil. Not everyone likes mayonnaise made entirely with olive oil, finding it too heavy; if you do like it, be aware that, according to Harold McGee, an extra virgin mayonnaise is likely to separate an hour or two after preparation. Groundnut oil is a possible substitute for the sunflower, as is rapeseed – although I am not terribly keen on the latter.
    3 • What to add when . Salt, stirred into the yolks initially, makes them more viscous, aiding the separation of the oil into little droplets. The mustard aids emulsification too. Some recipes tell you to add the vinegar at this stage, but it’s easier to incorporate the oil without it. However, you do need to thin the mayonnaise with vinegar or lemon juice once it becomes stiff, because the stiffness indicates that there is not enough liquid left to hold more oil.
    4 • Drop by drop . At first, you can emulsify only a tiny drop of oil. If you add too much, you’ll end up with some that has not been emulsified; then you’ll add more to it, and that won’t emulsify either. You’ll produce either a split liquid with oil and water separate, or a sauce in which the water is incorporated in the oil rather than the other way round.
HOLLANDAISE
    Hollandaise is scarier than mayonnaise, because you have to worry about heat as well. If the eggs get too hot, they will curdle. You need a double boiler, or a bowl that you can rest inside a pan so that the base of the bowl will not touch the water simmering below. Steam rising from the water heats the eggs gently.
    You can try making hollandaise in a saucepan on a direct flame; but it is a lot harder to manage this feat successfully than it is to warm custard in a pan ( see here ). In custard, the eggs are dispersed in milk and cream. With only eggs, butter and a little vinegar or lemon juice in your pan, you’ll have to work very carefully to stop the eggs catching on the base and curdling.
    This sauce goes wonderfully well with asparagus, and with poached fish. It’s not always practical: as you’ll see, it requires undivided attention, which you may not be able to spare if you have lots of other things on the go.
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HOW TO MAKE IT
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    Enough for 4 people
    3 tbsp vinegar
    2 egg yolks
    150g butter, cut into six pieces
    In a saucepan on the hob, boil the vinegar until it has reduced by a third. Bring water in a saucepan to a simmer, and turn down the heat so that the water merely shows bubbles rising to the surface. Place a bowl inside the pan, making sure that the base of the bowl does not touch the water. Put in the egg yolks and vinegar, 1 and start whisking. Add a piece of butter, and whisk it in until it has combined with the eggs; add some more; and so on. Continue whisking until the sauce thickens; turn off the heat immediately when it does. Add salt, and pepper if you like.
    Herbs go well with a hollandaise; tarragon, particularly so.
    You can hold the sauce for about 20 minutes above the hot water, provided that you whisk it from time to time.
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WHY YOU DO IT
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    1 • Helpful vinegar . It’s easier to add vinegar or lemon juice to a mayonnaise after you’ve incorporated a certain amount of oil. But in a hollandaise, the vinegar protects the yolks against the curdling effect of the heat (cf
McGee on Food and Cooking
). You could also add lemon