Melt the butter with the oil in a large
saucepan. Add the onions, stir well, cover and cook gently, stirring
occasionally, for 20 minutes.
When the onions are completely soft, add
the sugar and a pinch of salt and increase the heat to high. Cook for
about 2 minutes until the onions caramelize slightly.
Stir in the flour
and cook for 1 minute until light brown. Pour in the stock and wine, add
pepper to taste and bring to the boil. Lower the heat, partially cover
and simmer for 40 minutes.
Pile a little grated Gruyere on to each
round of toasted bread and brown lightly under the grill.
Add the Cognac to the soup. Stir well,
then taste and adjust the seasoning. Pour into heated soup bowls and
float the toasted breast on top. Serve immediately.
This famous soup is very sustaining,
partly due to the toasted slices of French bread with cheese that
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