Bring the water back to a boil and add the red potatoes and carrots. Cover, reduce heat to medium and simmer until tender.
Place meat in oven for approximately 15-20 minutes, checking periodically. A nice carmelized crust will begin to form on top of the meat. If the meat begins to burn, tent with foil for last few minutes. While the meat is finishing in the oven, do the following:
Once the potatoes and carrots are tender, and if you're making the boiled cabbage method, add cabbage and parsley to the water, continue to simmer, covered an additional 10 minutes or so, until the cabbage is tender. (If you are going to saute' your cabbage, my favorite method, just add the parsley here and see note below for sauteed cabbage instructions.)
Turn your vegetables off and:
Place meat on a serving platter or cutting board. Slice thinly, about ¼ inch thick.
Using a slotted spoon, remove vegetables into a serving bowl.
Serve meat with horseradish-sour cream mixture, vegetables, Irish Soda Bread and creamy soft butter, if desired.
Leftover meat is amazing the next day.