Portion the beef. Gently form the ground chuck into 4 loose balls (about 4 oz each); a ⅓-cup scoop works well. Don't overwork the meat. Chill while the griddle heats.
Preheat the griddle. Heat the Blackstone on medium-high for 8–10 minutes until it reaches about 400–450°F. Add the butter or oil and spread it thin.
Smash. Place each beef ball on the hot griddle. Lay a square of parchment on top and press firmly with a spatula or burger press until about ¼ inch thick. Peel off the parchment.
Season. Sprinkle the tops with salt, pepper, and the optional garlic and onion powders.
Sear. Cook undisturbed 2–3 minutes, until the edges are lacy and deeply browned.
Flip & cheese. Scrape under each patty, flip once, and top with a slice of cheese. Cook 1–2 minutes more, covering with a dome for the last 30–60 seconds to melt the cheese. Cook to an internal temp of 160°F.
Toast the buns. Butter the cut sides and toast on the griddle 1–2 minutes until golden.
Build & serve. Stack the patties on the toasted buns (double up for a true smash burger), add sauce and toppings, and serve immediately.