For the ranch dressing: In a medium bowl, whisk together all the mayonnaise, sour cream, lemon juice, honey, garlic and scallions. Season with salt and pepper. Set aside.
For the toppings: Heat a pan over medium heat. When warm, add the bacon and cook until slightly crispy, about 5 minutes. Remove from the pan and set aside on paper towels to drain some of the excess oil. In the same pan, add the slices of onion and cook until caramelized, about 20 minutes.
Preheat the oven to 350 degrees F.
For the patties: Combine the beef, veal, onions, garlic, Worcestershire sauce, 1/4 cup ranch dressing, capers, and chile flakes in a large bowl and mix well with your hands until blended thoroughly. Form into palm-shaped patties. Place 2 to 3 pieces of cubed cheese in the center of every patty and form the meat around the cubes so that they are entirely covered and in the center of each patty.
In a large pan, heat the vegetable oil over high heat. Sear both sides of the patties until brown, about 2 minutes per side. Top with the slices of cheese. Continue cooking in the oven until the cheese melts from the center of the patty, about 10 minutes.
To serve: Place the patties on the warmed buns and assemble with desired toppings.
Cook's Note : The ranch dressing keeps in the refrigerator for 3 days in an airtight container.