With six cups of milk, and each recipe requiring 3/4 of a cup of milk, we know instantly that she can make at least six potato casseroles, with milk left over. Each recipe has a 1/4 of milk left over. With the milk left over, which is 6 1/4 cups of milk, we can make a further two more with the milk we have. So in total, we can make 8 potato casseroles with the milf left over.