Scald milk, with onion and celery; strain into a pitcher and keep hot if convenient. Add to the remnants of cold boiled white fish enough canned salmon to make two cups; chop fine and rub through a purée sieve. Cook together in the blazer butter, flour, salt and pepper. Add the milk gradually, and, when all is added and the contents of the blazer are boiling, put a few spoonfuls of the sauce into the fish and beat until smooth; add more sauce, and, when well diluted and smooth, turn the whole into the blazer. Stir, and let cook until very hot; then serve with crackers, split, buttered, and browned in the oven. These proportions give three pints of soup. Vegetable purées may be prepared in the same way.