Preheat oven according to package directions for fries (we cook ours at 425°F). Bake for 25 to 30 minutes or according to package directions, then season with seasoning salt.

While the fries are baking, heat butter in a frying pan over medium heat. Add onions and cook for 5 minutes, then add 2-3 tbsp water. Cook for 6-8 more minutes until the water evaporates and onions turn golden, then add more water. Repeat adding water and cooking until the onions are soft and caramel in color, about 25 minutes total. Season with salt at end.

While the onions finish up, cook the burger patties on stove or grill until desired doneness, about 4 to 5 minutes per side or 8 to 10 minutes total. (Note: they will also be cooked more in the oven once the fries are assembled, so you could cook them slightly less at this stage so that they don’t overcook in the oven.) Cut the patties into bite-sized pieces.

Mix the sauce ingredients together in a bowl.

Top the cooked fries with burger pieces, then lay the American cheese on top of the fries. Bake the topped for 3-5 minutes or until cheese is melted.

Top the fries with the caramelized onions (note: if the onions are looking too clumpy, you can mix them with an extra splash of water at this time). Spoon some special sauce on top of the fries and top with pepperoncini, if using.