Chop the onion and celery and cook gently in the butter until golden brown. Peel, core, and slice the apples and add to the vegetables. Cook them in the oven for 20 minutes in a covered iron pan. Add the beef and chicken stocks, curry powder, paprika, and lemon juice. Season to taste and stir. Strain and bring to a boil. Take off heat and finally add the cream. Chill in the refrigerator if the soup is to be served cold. It is a pleasant surprise on a hot summer day when served chilled, and equally intriguing offered piping hot when the leaves begin to turn.