This section is from the book "The White Ribbon Cook Book", by Kathryn Armstrong. Also available from Amazon: The White Ribbon Cook Book.
4 potatoes, 2 leeks or onions, 2 oz. butter, pepper, 1/4 oz. salt, 1 pint milk, 3 tablespoonfuls tapioca.
Put 2 quarts of water into a stewpan, then take 4 potatoes, peel and cut in quarters, take also 2 leeks, wash well in cold water and cut them up; when the water boils put in potatoes and leeks, then add the butter, salt and pepper to taste, Allow it to boil to a mash, then strain the soup through a colander, working the vegetables through also; return the pulp and the soup to the stewpan, add one pint of milk to it and boil; when boiling sprinkle in by degrees tapioca, stirring all the time; then let it boil for 15 minutes gently.
 
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