Preheat your oven according to the package instructions for the French fries, or heat your oil in a deep fryer if you prefer frying. Lay those frozen fries in a single layer on a greased baking sheet or drop them carefully into hot oil. You'll want them golden brown and crispy—this is crucial.

While the fries cook, it’s time to whip up the sauce. In a medium bowl, combine the mayonnaise, mustard, pickle relish, vinegar, and smoked paprika. Stir until well mixed. This creamy concoction is your secret weapon.

In a separate pan, heat 2 tablespoons of vegetable oil over medium heat. Add the finely diced onions, sprinkle with a bit of kosher salt, and cook them until they become translucent and start to caramelize, stirring occasionally. This should take about 8-10 minutes.

Once your fries are cooked, place them on a serving platter. While they’re still hot, sprinkle the fries with salt to taste. Immediately drape the slices of American cheese over the fries, allowing it to melt slightly.

Spoon generous amounts of the prepared sauce over the cheesy fries. Top it all with those beautifully caramelized onions. If you’re feeling fancy, finish with a sprinkle of chopped chives for an extra layer of flavor.