Put the butter and oil in a saucepan and cook on a gentle heat til the butter foams die down. Add the cougettes which you have chopped and diced and add garlic if you wish - cook gently and stir occasionally until courgettes go slightly tranluscent. Add enough beef stock to just cover the tops of the vegetables. Cook gently for about 15 mins max (don't let the veg get too mushy). Take off heat and blend with an electric blender - add some cream (either double or single) and blend to a fine consistency - not too thick. reheat a little and serve in hot soup bowls.
The recipe was given to me by a French family friend from Revel in the south of France.