St. Patrick, the apostle and patron of Ireland, died in A.D. 461. He was greatly venerated from early times. At the famous shrines of Lough Derg in Donegal and Croagh Patrick in Mayo he is honored by the hard and almost heroic penance the faithful perform in imitation of his own fasting, mortification, and prayers.
In the course of centuries the veneration of St. Patrick also became identified with the patriotic and national ideals of the Irish people. Thus, March 17 is not only a religious holy day for them but their greatest national holiday as well. The popular celebration on St. Patrick's Day consists of traditional details which have also found their way to the New World: attendance at Mass in the morning, a solemn parade with subsequent meetings and speeches, festive meals in the home, and an evening of entertainment.
During the time of suppression by the English, the common people of Ireland were quite poor indeed, and many of them did not have enough food supplies left over from the previous harvest for the feast. They had to resort to their all-year staple-potatoes in order to "stretch" the festive meal. Thus, potato dishes became a traditional part of St. Patrick's Day dinner, and for many other feast days, such as Halloween/All Saints Day.
Cook potatoes in boiling salted water in saucepan; mash; set aside.
Cook cabbage in boiling salted water in saucepan; mash; set aside.
Sauté onions in 2 tablespoons butter in a deep saucepan for 5 minutes. Add potatoes, cabbage, salt, pepper, milk. Beat until well blended and smooth. Place piece of butter on top of each portion when serving. Eat with spoon from outside in, dipping each bite into melted butter.