The spleen is an organ in the upper left abdomen, which filters blood, disposes of worn-out red blood cells, and provides a 'reserve supply' of blood. It contains both red tissue, and white lymphatic tissue. The major (encapsulated) lymphatic organs are the lymph nodes, thymus and spleen.
Place the brined corned beef in a large pot or Dutch oven along with the liquid and spices that accompanied it in the package. Pour in enough water to cover the beef, then bring the water to a boil on the stovetop. Reduce the heat to a simmer, and cover the pot. A three-pound corned beef could take three hours or more to become perfectly tender. Check the meat occasionally, adding more water if necessary. The beef is ready when it pulls apart easily.
Add the butter or bacon fat to a large pot and bring it to medium-high heat. Season the beef with a few dashes of salt and pepper. When the butter or bacon fat has melted and is just beginning to bubble with heat, add the cubed beef and sear it for one to two minutes on each side. Remove the beef cubes from the pot and set them aside. Add the onions and garlic to the pot and saute them for four to five minutes, until they are softened.