Preheat the oven to 400°F (200°C) and grease a baking pan with non-stick cooking spray, or line it with parchment paper.
In a mixing bowl, combine the ground beef, dried minced onion, salt, and black pepper. Mix well until all the ingredients are evenly incorporated.
Transfer the meat mixture onto the prepared baking sheet and press it into an even layer, covering the entire sheet.
Bake in the preheated oven for about 15-20 minutes, or until the meat is cooked through and browned on top.
Remove the baking sheet from the oven and carefully drain any excess grease.
While the meat is still hot, slice it into 12 equal-sized squares, resembling the classic White Castle patty shape.
Split the slider buns and place them on another baking sheet, cut side up. Toast them in the oven for a few minutes until lightly golden.
Place a square of meat on the bottom half of each bun.
Top each patty with a slice of American cheese and pickle slices.
Cover the sliders with the top halves of the buns.
Serve the White Castle Sliders immediately while they're warm and enjoy!
Notes
Dried minced onion can be found in the spice aisle of most grocery stores and adds a subtle onion flavor to the meat mixture.Adjust the amount of salt and black pepper to your taste preferences.Greasing the baking pan or using parchment paper will prevent sticking and make it easier to remove the cooked meat mixture.Make sure to drain any excess grease from the meat after baking to keep the sliders from becoming too greasy.Slicing the meat into squares while it's still hot will help maintain the shape of the classic White Castle patties.Toasting the slider buns in the oven adds a nice crunch and helps hold up to the juicy meat and toppings.Leftover sliders can be stored in an airtight container in the refrigerator for up to 3 days. Reheat them in the microwave or oven before serving.