What ingredients are required to make bubble and squeak?

Bubble and Squeak is a very old, traditional Irish meal. My "Irish Family Food" cookbook, by Ruth Isabel Ross (published by Gill & Macmillan, Ltd., Goldenbridge, Dublin 8) has this recipe listed under Ways with Potatoes. "This was surely invented as a way of using up left-over cabbage. It is called bubble-and-squeak because the vegetables are boiled first or bubbled. They then squeak after they are fried. If care is taken and the mixture is cooked to a golden-brown crispness, it is attractive to young appetites."

Here is the recipe: Serves 2 450 g/1lb potatoes, peeled; 175 g/6 oz cooked cabbage, chopped; salt and pepper; butter or margarine for frying. This tastes better if the potatoes are freshly cooked. Steam or boil, dry off and then MASH the potatoes. Add the chopped cabbage and seasoning. Do not add milk, as it will leak into the frying pan. Press the potato and cabbage mixture into one or two 'cakes' for each person. Fry these until there is a crisp brown skin on both sides. Serve at once.