Scrub and cut the potatoes into quarters, and place in a large pot of water. Bring to a boil, and cook until potatoes are tender.
Place the cabbage, onion and water in a large pot and turn heat on to high. When the water starts to boil and sizzle (about a minute), cover the pot with a lid and reduce heat to low, and cook for about 8 minutes until they are tender, not mushy.
Using a potato ricer, press the potato into the pot of cabbage and onion until all of the potato pieces have been pressed (remove the skins between pressings). Add the butter, cream, salt and pepper and gently mix until it is thoroughly combined. Taste to see if any more seasoning is necessary.
Serve warm. If desired, wrap the coin, ring, and button in some paper to tuck under the colcannon (you don't want your guests to choke)!