Soupe à l’oignon gratinée
1kg onions, thinly sliced
1 heaped teaspoon sea salt
1 level tablespoon plain flour
125ml dry vermouth
1 litre beef stock
Plenty of freshly ground white
For the croûtes
1 small baguette
1 large clove garlic, peeled
25g softened butter
50g grated Gruyère
For finishing the soup and glazing it
30g-40g extra grated Gruyère
Pre-heat the oven to 200˚C/gas mark 6. Take a large pot and in it melt the butter. Tip in the onions and salt and allow the onions to collapse over a moderate heat, covered and stirring occasionally.
Once they have flopped down and become slippery-about 30 minutes-turn the heat up a touch and cook, uncovered, for a further 20 minutes or so, stirring often. The end result should be when the onions have become really golden brown and sticky; almost a thick smear on the bottom
of the pan.
Stir in the flour and cook for a further 5 minutes until well mixed in. Add the vermouth, stock and pepper and stir together. Bring up to a simmer and skim off any unsightly scum that will rise to the surface. Simmer quietly for a further 20 minutes; it should be rich and full of onion flavour, so cook a touch longer if it’s not.
While the soup is doing its thing, make the croûtes. Rub the baguette all over with the garlic clove until it’s almost exhausted. Slice the baguette into thick-ish slices, then smear a shallow baking tray-one that will roughly take the slices in one layer, quite snugly -with the butter. Lay on the bread slices and strew with the cheese.
Bake in the oven for about 15-20 minutes until bubbling and blistered. Remove, allow to cool and then lift them off and separate one from the other; the cheese will have welded them together. Turn the soup up to 220˚C/gas mark 7.
To finish the dish, choose a large and shallow, oven-proof pot that will be almost full when the soup is poured into it. Distribute enough croûtes over the surface to completely cover it, then sprinkle with the extra cheese. Bake until ferociously hot, bubbling around the edges and the surface is blistered with pustules of melted cheese.
It is authentic if some of the soup dribbles over the edge and sizzles down the sides of the pot, so have a sheet of foil ready beneath. Ladle into shallow soup plates and eat when it’s safe to so do.
For the pastry
100g plain flour
65g cold butter, cut into cubes
1-2 tbsp iced water
For the filling
500g onions, peeled and very thinly sliced
3 sprigs thyme, tied together with string
2 egg yolks
125ml whipping cream
75ml soured cream
Salt and freshly ground white pepper
Using a food processor, blend together the butter, flour and salt until it resembles fine bread crumbs. Now, tip into a large, roomy bowl and gently mix in the water with cool hands or a knife, until well amalgamated. Knead together, then put into a plastic bag and chill in the fridge for at least one hour before rolling.
Pre-heat the oven to 180˚C/gas mark 4, and place a flat baking sheet on the middle shelf; this helps the base of the tart to cook thoroughly. Melt the butter in a wide, solid-based shallow pan. Tip in the onions, tuck in the tied-up thyme sprigs and very gently sweat over a moderate heat for about 30 minutes, stirring occasionally, or until pale golden and completely soft. Cool.
Roll out the pastry as thin as you dare, then line a 20cm by 3cm deep tart tin, prick the base and blind bake. This is achieved by lining the uncooked pastry case with a sheet of tinfoil and filling with some dried haricot beans, for instance. Cook for about 15 minutes and remove from the oven.
Carefully lift out the foil and beans and transfer to a bowl or tin for future use. Return the pastry to the oven for a further 15 minutes, or until it’s crisp and well cooked through, particularly the base.
Beat together the egg, egg yolks and both creams until well amalgamated. Carefully mix the onions with this mixture, check for seasoning, carefully pour into the pastry case and gene-rously grate some nutmeg over it. Bake in the oven for about 40 minutes or until it’s pale golden and just firm to the touch.
Leave for 15 minutes before removing from the tart tin. Best eaten warm, or at room temperature.
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