Place ground chicken, bread crumbs, ranch dressing mix, and dried minced onion in a medium bowl; gently mix. Shape into 4 meatballs. Cover with plastic wrap and refrigerate 30 minutes. Meanwhile, cook bacon to desired crispiness; set aside.

Preheat a charcoal or gas grill for direct cooking over high heat. Place a large cast-iron griddle on grill rack to preheat. Remove meatballs from refrigerator; sprinkle with kosher salt and black pepper. Place meatballs 1 inch apart on hot griddle. Sear for 30 seconds. Smash burgers to ¼-inch thickness using a large spatula. Cook 6 to 8 minutes or until edges begin to brown. Turn burgers over; place 1 slice dill Havarti cheese on top of each patty. Cook 2 to 3 minutes more or until cheese melts and burgers reach 165°.

Butter and toast buns. To assemble, place a burger on each bun bottom; top with tomato slices, lettuce leaves, bacon, prepared Hy-Vee ranch salad dressing, and bun top.