BAKE THE POTATOES
Preheat oven to 425°F.
Wash and dry the potatoes well, then pierce each one a few times with a fork.
Rub all over with neutral oil and season generously with salt only.
Place directly on a baking sheet or oven rack and bake for about 45 to 60 minutes, flipping halfway through, until the skin is crispy and the inside centeris fork tender.
MAKE THE BURGER SAUCE
In a small bowl, mix together mayonnaise, pickle relish, ketchup, and sugar.
Stir until smooth and set aside.
MAKE THE CARAMELIZED ONIONS
Heat neutral oil in a pan over medium heat.
Add the diced onion and salt, stirring occasionally.
Cook for about 15 to 20 minutes, until soft, golden, and deeply caramelized.
Add water a tablespoon at a time if needed to prevent sticking and to deglaze the pan as they cook down.
Remove from heat.
COOK THE GROUND BEEF
In a large skillet over medium-high heat, melt butter.
Add ground beef and season with salt and pepper.
Stir in Worcestershire sauce, beef broth, and yellow mustard.
Cook, breaking up the beef, for about 6 to 8 minutes until browned and fully cooked.
Divide into portions in the pan, top each with American cheese, and let it melt, about 1 minute. Remove from heat.
ASSEMBLE
Once everything is ready, slice open the hot baked potatoes.
Fluff the inside with a fork and add butter, salt, and black pepper to taste. Mix again.
Spoon the cheesy ground beef into each potato.
Top with caramelized onions, dill pickles, chopped pepperoncinis, and parsley.
Drizzle generously with burger sauce and enjoy warm!