01 -
Start off by tossing onions, salt, butter, and oil in a pan on medium-low. Let them cook down slowly and give a stir now and then. If they start to brown too fast, turn the heat down. Go for about 30 minutes so they’re nice and golden brown.
02 -
Grab a bowl and mix mayo, ketchup, relish, vinegar, sugar, and chili flakes if you like a kick. Stir everything together so it’s smooth and pop it aside for now.
03 -
Pop those frozen fries in the oven or into hot oil, whichever way you like. Let them cook until they’re crunchy and have a good golden look.
04 -
Spread your hot fries over a platter. Lay on the cheese slices or scatter your shredded cheddar, then stick under the broiler for three to five minutes till the cheese is oozy.
05 -
Pile the caramelized onions all over the melted cheese, pour the sauce across the top, and dig in right away.