There are so many packages of corned beef stacked in supermarket meat cases this week, you’d think the whole world was Irish. It’s a fatty cut, which is the reason everyone loves it - and loaded with flavor. In recent years, bright red corned beef, made with enough preservatives to keep the red intact during the long simmer, has fallen out of favor. This is the meat of everyone’s childhood - stringy, so rosy it looks stained by beets, and perfectly delicious. Corned beef without preservatives is known as “gray,’’ and once you get over the idea that the centerpiece isn’t flame-colored, you can settle into a plate of nicely seasoned meat (the flat cut of brisket is less fatty) surrounded by carrots, cabbage, rutabagas, and golden potatoes.