White Castle Cheeseburger Slyders (Copycat) - cooking recipe

Ingredients

ONION
1 medium onion, finely minced
2 tablespoons water
3/8 teaspoon salt
BEEF
3/4 lb fresh 80% lean ground beef
1 1/2 tablespoons water
3/8 teaspoon salt
1/8 teaspoon ground black pepper
CHEESE
12 slices kraft deluxe American cheese
PICKLE
36 -48 slices heinz hamburger dills
BUN
12 sara lee classic dinner rolls
CONDIMENTS (White Castle condiments vary by region)
prepared yellow mustard or spicy brown mustard
tomato ketchup

Preparation

FINELY mince one medium onion by hand, or by pulsing in a food processor; PLACE onions into a heavy-bottomed non-stick or stainless steel skillet; ADD 2 tablespoons water and 3/8 teaspoon kosher salt; COOK onions over medium heat until onions are translucent and most water has evaporated (replenish water if necessary to keep onions just moistened); SPREAD onions evenly and levelly in a 15 x 12 baking sheet; LOOSELY cover; PLACE sheet of onions into freezer until almost frozen, adhering to bottom of baking sheet.
START with a clean oven; PLACE oven rack in the lower 1/3 position; PREHEAT oven to 500\u00b0F ; In a medium bowl, mix 3/4 lb ground beef with 1 1/2 tablespoons water, 3/8 teaspoon salt and 1/8 teaspoon ground black pepper in a medium bowl with a fork until thoroughly combined; DUMP ground beef mixture onto a COVER ground beef mixture with a sheet of waxed paper; PRESS ground beef mixture into the baking sheet with onions evenly to the edges using hands first, then with a rolling pin if desired, for uniformity; REMOVE waxed paper and discard.
CUT ground beef lightly into 12 symmetrical squares using a pizza cutter (3 across x 4 down) leaving meat intact; POKE 5 evenly-spaced holes into each beef patty square (resembling the 5-dot pattern of standard playing dice), with a thin wooden spoon end or drinking straw, pressing while twisting to bore holes.
PLACE squeezable ketchup and/or mustard, sliced pickles and sliced cheese within easy reach in work station to assemble Slyders quickly when needed; TRIM or cut American cheese to fit Slyders (I usually trim the edges only, but to economize you may cut cheese slices into 4 small portions).
DIVIDE one package (12) Sara Lee Classic Dinner Rolls using a sharp knife for crisp clean edges; CUT each roll to a 1/3 slice for the bottom half, leaving 2/3 for the top bun; REPLACE bun tops; ARRANGE buns on a clean platter.
INSERT a second baking sheet, inverted, over prepared baking sheet with meat and onions to prevent spatter and to help steam; CAREFULLY transfer the baking sheets containing beef mixture into preheated oven wearing oven mitts; CLOSE oven door.
STEAM-BAKE beef patties for about 7-8 minutes or until beef is no longer pink (patties will shrink slightly upon cooking); REMOVE from oven; MOVE baking sheet with cooked patties into work station.
LIFT each beef patty with a slotted spatula and place over bottom buns; PLACE a slice of cheese over each onion-topped meat patty diagonally; ARRANGE dill pickle slices over cheese.
SQUEEZE 1 teaspoon mustard OR 1 teaspoon ketchup evenly onto inner TOP bun; PLACE one meat patty over each BOTTOM bun using a slotted spatula; SET bun tops atop assembled Slyders.
WARM prepared Slyers on platter in microwave at 100% power only until warmed and cheese has melted (about 15 seconds); SERVE warm Slyders immediately and enjoy!