Melt 75g / 3 oz of the butter in a large heavy-based pan. Set about 200g / 7 oz of the onions
aside and add the rest to the pan with the bay leaf. Stir to coat in the butter, then cover and
cook very gently for about 30 minutes. The onions should be very soft and tender, but not
Add the vermouth, increase the heat and boil rapidly until the liquid has evaporated. Add the
stock, 5ml / 1 tsp salt and pepper to taste. Bring to the boil, lower the heat and simmer for 5
minutes, then remove from the heat. Leave to cool, then discard the bay leaf and process the soup
in a blender or food processor. Return the soup to the rinsed pan.
Meanwhile, melt the remaining butter in another pan and cook the remaining onions slowly,
covered, until soft but not browned. Uncover and continue to cook gently until golden yellow. Add
the cream to the soup and reheat it gently until hot, but do not allow it to boil. Taste and adjust
the seasoning, adding a little lemon juice if liked. Add the buttery onions and stir for 1-2
minutes, then ladle the soup into bowls. Sprinkle with croutons or chopped chives and serve.