Nigel Slater, TV cook, bestselling cookery author and food columnist for The Observer, has joined the RHS grow your own campaign.
In this series, Nigel focuses on the best produce for growing and cooking.
Nigel's onion recipes
Discover Nigel's onion recipes for September:
Onions
Nigel Slater enjoys the different aromas that onions bring to the kitchen, and suggests ways of storing freshly harvested bulbs.
Someone, or perhaps I should say ‘something’, has dug up almost every onion I have ever planted. I have yet to catch them, but I cannot help but wonder if it is the same four-legged joker who tends to move my tulip bulbs around the garden.
It is hard to think of life in the kitchen without the gentle, sweet-savoury note of onions. They form the backbone to so much of our cooking, especially autumn and winter recipes. Though some gardeners grow from seed, most plant immature onions known as ‘sets’.
The cultivars you choose depends on how you intend to use them (they are all derived from Allium cepa). Smaller, tight-skinned selections such as ‘Sturon’ and ‘Copra’ are good all-round kitchen onions; red-skinned cultivars such as ‘Red Baron’ keep less well but have a mildness that appeals to many cooks. Shallots such as ‘Pikant’ or Jersey long types such as ‘Longor’ have a gentle enough flavour for salads and sauces. Spring onions, such as my favourite ‘Noordhollandse Bloedrode’ (syn. ‘North Holland Blood Red’) are easy to grow, and the thinnings offer a mild flavour to salads.
For gardeners with a row or two in the vegetable patch, late summer and early autumn is the time to lift, dry out and store them for winter. A few sunny autumn days are what you need for drying freshly harvested onions; lie them somewhere warm and airy, covered from the rain with a cloche if needs be. Dried out, they will keep in good condition for many weeks, even months.
Stored onions hate damp, which will make them rot. If kept in a dry place they should last through to spring, by when even the firmest will have started to soften. Good air circulation is key, which is why they store so successfully tied into the long, plaited strings of French onion sellers.
Using onions
Onions change dramatically when cooked. A raw bulb that is pungent, almost sour to eat uncooked can, with the application of heat, become intensely sweet. To bring this, and add body, is their role in soups and stews – the trick is to cook an onion slowly, allowing its natural sugars to caramelise. Cooked too quickly, or over too high a heat, they can burn and introduce bitterness to a dish.
Some of us cry when we prepare an onion because of a volatile ‘lachrymatory’ (tear-inducing) chemical containing sulphur that dissolves in our eyes to form weak sulphenic acid, hence the irritation. I am one of those who has to get out a handkerchief within seconds of starting to chop. I have tried every possible remedy, including holding a piece of bread in my mouth and a few equally odd, desperate measures, all to no avail. A really sharp knife helps (the juice seems to spurt less), but little else I have tried makes a difference. Cooking gets rid of the volatiles, producing sweet bispropenyl disulphide instead.
No matter how much this vegetable makes me sob it is still as important a part of my kitchen as lemons or garlic. Onion’s ability to act as an aromatic, forming the base notes on which we build a stew or a soup is so common we almost take it for granted, but I also value it as a vegetable in its own right. A whole onion baked till soft and golden is a fine supper, served in all its buttery simplicity, or under a blanket of cheese sauce. Simply peel and boil the onions whole until tender to the point of a knife, then put them in the oven with butter and few herbs such as thyme or rosemary. Roast for 40 minutes and they emerge golden and sweetly scented; they are also wonderful with roast beef.
I find onions tend to accumulate in my larder – I rarely manage to use up one batch from the weekly organic box delivery before another arrives. To rid myself of gluts I make large pots of soup. The mellow smell wafting through the house is the essence of autumn, and the soup seems to improve for a few days in the fridge.
Spring onions and shallots have their place in the kitchen, but it is the classic, tight-skinned common onion that I find most useful. I have never taken to eating them raw and finely sliced, as others do, but I would honestly question my seriousness as a cook if I didn’t have at least one in the house. I only wish I could keep them in their right place in the garden.