First, in a large skillet or flat top cooker over low to medium heat, add your sliced onions to a bit of oil and cook until they start to turn translucent. Then, sprinkle ion your brown sugar and a pinch of salt and continue to cook the onions slowly so the onions caramelize without burning.
Meanwhile, in a mixing bowl, whisk together your mayo, ketchup, Worcestershire, pickle juice, chopped pickles, smoked paprika, onions powder, and garlic powder until they are well combined. Season with salt and pepper to taste, then set the sauce aside.
Then, place your uncooked beef in your skillet along with the seasonings and Worcestershire and cook until browned. I spread my meat onto the flat top, allowing the meat to cook on one side before breaking the meat apart. This gave the meat a broken patty texture.
After that, butter or spread mayo on each slice of bread. In a clean pan over medium heat, place a slice of bread buttered side down, and layer on your cheese, beef, another slice of cheese, and caramelized onions. Then, add your final slice of bread on top, butter side up.
Once the bottom turns golden, flip the sandwich carefully and continue toasting until the second side is golden and the cheese melts completely.
Finally, remove the patty melt from the pan, cut in half, and serve immediately with the sauce on the side for dipping.