St. Patty's Leftover Treat -- Bubble and Squeak

I am cooking up a batch of Bubble and Squeak for lunch with the sweetheart.  Bubble and Squeak uses the leftover veggies from your St. Patty's Day feast.  (Our's was a doozy this year).   It is simple and fun.  It gets it's name from the noises the pan makes as the treat cooks in it's black cast iron pan.  Here is how you make it:

Take a good amount of butter (I used 3 T) and melt it in a cast iron pan. (Has to be a cast iron pan).  Dice some onions and cook it in the pan.  Mash up your left over potatoes, carrots, turnips.  Whatever you had in the pot with your corned beef or smoked pork butt.  Slice up your left over cabbage and mix it with the veggies mash.  Put it into the pan, mash it down and cook for 10 or 15 minutes until it is nice an brown on one side.  Flip it out on a cutting board, slide it back in the pan and brown the other side.  Eat it with butter, malt or cider vinegar, salt and pepper.  Enjoy!