Heat griddle to about 375-425℉ over medium heat. *If using a skillet, heat a large skillet over medium heat. At the same time, preheat oven to 400℉.
Add about 1 tablespoon of cooking oil to the heated griddle surface and spread it around with your spatula. Add the diced onions to the oiled griddle and sauté until translucent. Season onions with salt and pepper, and move them to the cooler zone on your griddle to keep warm while the steak cooks. *For skillet cooking - sauté diced onions over medium heat until translucent. Season with salt and pepper, then transfer to a bowl while you cook the steak.
Add the thinly sliced ribeye steak to the griddle in a thin even layer. Allow to cook on the first side for about 1-2 minutes to develop a bit of crust. Then, using your spatula with one hand, hold a few pieces of steak in place as you use the bench scraper in the other hand to "chop" the steak slices. As you're chopping the meat, you will use the scraper to kind of pull the steak away from the spatula in one fluid motion. *NOTE - If you're making cheesesteaks in a stovetop skillet, I recommend cutting the sliced ribeye into bite-sized pieces before adding it to the skillet to cook. When the steak is all chopped, continue to cook on the griddle stirring often, just until all of the pink is gone from the meat. Do not overcook.
While the steak finishes cooking, add 2 tablespoons butter, 2 cloves minced garlic, and 1 tablespoon Worcestershire sauce to a small saucepan. Heat until butter is melted, stirring occasionally. Set to the side.
Season the steak with salt and pepper or your favorite all purpose seasoning. Add the sautéed onions to the steak. Mix together briefly, then transfer to the cooler side of the griddle. Or for skillet cooking, remove from the heat.
Leave King's Hawaiian rolls in one large sheet of 12 rolls, and cut in half horizontally using a serrated knife. Butter the cut sides of the sheets of rolls, and toast on the griddle until golden brown.
Transfer the bottom of the toasted rolls to a baking sheet. Place the provolone cheese slices evenly across the bottom buns, overlapping the cheese a bit if needed. Top the cheese slices with the cooked steak and onion mixture. Place the sliced American cheese on top of the steak layer, and then top with the tops of the rolls.
Brush the tops of the sweet rolls with the butter, garlic, Worcestershire mixture from step 5. Bake in the oven at 400℉ for about 12-15 minutes, or until the tops of the rolls are golden brown and the cheese is melted.
Serve Philly cheesesteak sliders warm. Optional toppings include sliced banana peppers, pickled jalapeños, mayo, etc.