Tom Parker Bowles's favourite recipe: French onion soup

There are varying degrees of extreme heat. The melting point of pure gold is, for example, a fairly brow-beading 1,064˚C. And the centre of the sun, properly sizzling, is nearly 15 times that. But both seem positively glacial when compared with the ideal temperature of French onion soup.

For this is a dish that must be borne to the table on an asbestos salver, hot as a heatwave in Hades, its lava-like liquid — all buried beneath a bubbling morass of molten cheese — seething like an incandescent phoenix. The first sip should blister the tongue and ravage the roof of the mouth. This pain is all part of the pleasure — there’s nothing more depressing than tepid onion soup.

Because this dish is no mere Gallic broth, rather pure bonhomie in a bowl, a boozy, beefy, allium-scented masterpiece that cries out for the chill depths of winter. It does not, however, suffer fools gladly. Not so much in the eating (a spoon is the only weapon you’ll require), as the cooking. ‘The amount of onions — enormous — is the key to a good onion soup,’ note Simon Hopkinson and Lindsey Bareham in their retro-scented masterpiece The Prawn Cocktail Years. This is a recipe that demands time and attention, too. ‘Patience is all,’ they continue. ‘A beady eye is also needed or the onions soon scorch as they flop down into the bottom of the pan.’

It’s that slow transformation, from cold, hard onion to a soft mess of golden brown (texture like sun), that lies at the heart of this soup. Ignore any fool who tells you that caramelisation can be done in 20 minutes. Utter rot. For me, it takes an hour at the very least. First, a gentle sweat of thinly sliced alliums in butter, over the most flickering of flames, in a covered, heavy-bottomed pot.

Then the lid is removed, the heat slightly increased and the alchemy begins, for 45 minutes, if not longer. Stir regularly and stay vigilant. As to the variety of onions, the usual Spanish will do, but if you can get hold of those pink Roscoff onions from Brittany (you can find them at www.natoora.com and Waitrose, too), so much the better. They are as silken as they are sweet.

Some recipes call for chicken stock, which makes for a decent dish. Yet it does rather miss the point — this soup is all about bullish, swaggering bovine heft and, if onions are its soul, then beef is its heart. Stock cubes have no place here — use the best fresh stuff you can find. Better still, make it yourself. Booze is key, too, and I like a mixture of white wine and sherry. Cider is also traditional — and excellent — whereas a glug of Cognac or even Calvados (added right at the end) is positively medicinal.

The bread, preferably a sliced, proper baguette, should be a little stale and toasted before being rubbed with garlic and floated atop the soup. This gives the bread a little more buoyancy, meaning it will hold up better when weighed down with cheese. Gruyère is the classic choice, although Comté and good Cheddar will do. Blue cheese, on the other hand, most certainly will not.

Serve in individual ovenproof bowls. Or simply bang it on the table in the Le Creuset pot, to be shared among the ravenous masses. Whatever you do, remember that the surface must be smothered in a thick blanket of blistered, burnished cheese. Even a glimmer of broth is a sure-fire admission of defeat.

French Onion Soup

I’ve adapted this from a recipe in The New York Times, which was first published in 1954. Rather serendipitously, it popped into my inbox as I was starting to write the column. I like its classic simplicity.

Ingredients

Serves 4

60g unsalted butter
3 to 4 large red or yellow onions (about 1.5kg), peeled and thinly sliced
¾tspn sea salt, plus more to taste
1½ litres beef stock
200ml dry white wine
Good glug of dry sherry
1tbspn plain flour
½tspn black pepper, plus more to taste
8 slices of baguette or sourdough, about a day old, toasted
1 clove of garlic, peeled
200g grated Gruyère cheese

Method

1 Melt butter in a heavy-bottomed pot (Le Creuset is ideal) over a low heat. Add onions and half a teaspoon of salt, stir and cover, letting onions soften for 10 minutes.

2 Remove lid and let onions caramelise until golden brown over a medium heat, stirring regularly. Adjust heat if onions are browning too quickly. The caramelisation process may take 45–60 minutes, sometimes more.

3 Meanwhile, warm beef stock in a saucepan over a low heat. Once onions are caramelised, add wine and sherry to the pot and allow mixture to come to the boil. Stir in flour and let thicken for a minute or two.

4 Slowly add warm stock, a quarter teaspoon of salt and the pepper to the onion mixture and simmer uncovered for 15 minutes. Add more salt and pepper to taste.

5 Toast the bread slices and rub them with garlic.

6 Heat the grill and arrange individual ovenproof casseroles on a baking sheet. Ladle soup into casseroles and cover top with bread slices. Sprinkle each casserole generously with Gruyère. Or you can use the pot in which the soup is cooked and serve it at the table. Grill under a high heat for a minute or two, watching carefully, until cheese bubbles and browns. Serve immediately.