Curds are a dairy product made by curdling milk with rennet or yeast so that it separates , and taking away the liquid part ( called whey ) . Milk that has been left to go sour will also naturally separate into curds and whey . In England , curds produced from the use of rennet is referred to as junket , with true curds and whey only occurring from the natural separation of milk due to its environment ( temperature , acidity ) .