Wash the celery and onion and cut into fine pieces. Then place them in a porcelain-lined saucepan and let boil for about a half hour. Take off and mash, and press through a colander. Set the milk to boil in a farina boiler, and as it heats well, add to it the water and Celery that has been pressed. Rub smoothly together the flour and butter, and then stir into the boiling Soup, stirring constantly till it thickens to a cream of the right consistency. Add salt and pepper to taste and serve hot. It is very delicious served with slices of delicately toasted and buttered Croutons. Serve on a separate dish and garnish with sprigs of parsley and slices of hard-boiled eggs.