Copycat Animal Style Fries + Animal Style Sauce

Caramelize the onions. Add the butter to a medium skillet over medium heat, allow the butter to melt and sizzle. Once sizzling, add in the onions and saute until soft and fragrant (about 3-4 minutes). Add the water and salt and keep sautéing until the onions have softened completely and most of the water has evaporated. Sprinkle with sugar and saute until caramelized and browned (2-3 minutes). You may add more water to keep the onions from sticking, if needed.
Make the Animal Style sauce. In a medium bowl, add the mayonnaise, ketchup, pickle relish, sugar, and vinegar. Mix until fully combined and set aside.
Prepare the fries. If using frozen, cook according to package instructions. If using McDonald's fries, reheat until hot (if desired). If using homemade, make your own french fries!
Assemble the Animal Style fries! Place your hot french fries in a large baking dish or a non-stick pan and top them with the cheese, caramelized onions, and sauce. Make sure the fries are hot or the cheese won't melt! Serve and enjoy!
If needed, you can top the fries with the cheese and then bake at 350F (180C) for 5-10 minutes or until the cheese has melted and then top with onions and topping. Serve immediately.