I cook the cornbeef in boiling water in which I've added some vinegar, sugar and herbs (either mixed or bay leaves or both). Having the meat hot is desireable, but you can let it cool in the water to enhance the flavour. Potatoes and then cabbage are added to the water when the meat is done (or nearly done).
Sorry I con't give you amounts of ingredients as I guess work it according to size of the meat.