Combine butter, Worcestershire sauce, and fish sauce in a medium bowl. Add ground beef; gently mix. Shape into 4 meatballs. Cover with plastic wrap and refrigerate for 30 minutes. Meanwhile, preheat a charcoal or gas grill for direct cooking over high heat.

Place a large cast-iron grilled on grill rack to preheat. Remove meatballs from refrigerator; sprinkle with Hy-Vee kosher salt and Hy-Vee coarse-ground black pepper. Place meatballs 1 inch apart on hot griddle. Sear for 30 seconds. Smash burgers to ¼-inch thickness using a large spatula. Turn burgers over; place 1 slice of cheese on top of each patty. Cook 1 to 2 minutes more or until cheese melts and burgers reach 160°.

Butter and toast 2 split Hy-Vee Bakery sesame seed hamburger buns. To assemble, place a lettuce leaf on bun bottoms' top each with 2 burgers, pickle slices, red and yellow tomato slices, red onion, ketchup, and bun top.