Preheat oven to 350°F.
Mix beef with salt, pepper, garlic powder, onion powder, and Worcestershire.
Taste and adjust the beef seasoning with salt or garlic powder.
Form 12 small patties; cook in a skillet 2–3 minutes per side.
Mix mayonnaise, ketchup, and mustard for the sauce.
Slice rolls; layer bottom halves with sauce, patties, cheese, onion, pickles, and top halves.
Brush tops with the butter and sesame seeds; bake covered 10–12 minutes.
Serve on a white ceramic platter with parsley.