In a large mixing bowl, combine the ground beef, diced onions, Worcestershire sauce, black pepper, and salt. Mix gently with your hands or a spoon, being careful not to overwork the meat, which can result in tough sliders.
Divide the beef mixture into 12 equal portions and flatten each portion into thin patties, about 1/4 inch thick. The thinner they are, the more they will resemble the classic White Castle sliders.
Heat oil in a skillet or griddle over medium-high heat. Once hot, add the patties to the skillet. Cook for about 2-3 minutes on one side, then flip and cook for an additional 2 minutes. During the last minute of cooking, place half a slice of cheese on each patty to melt.
Place each cooked patty on a slider bun. Top with two dill pickle chips for that signature crunch. You can also add extra diced onions if you prefer!
Serve the sliders warm with your favorite sides, like fries or onion rings. These sliders are best enjoyed fresh but can be stored for later.