01 -
Pile those golden onions over your cheesy fries and pour as much sauce as you like on top before digging in.
02 -
Lay your cooked fries on a platter, scatter the cheese all over, and put them under the broiler for about 3 to 5 minutes. Take them out when everything's nice and melty.
03 -
Get your fries crispy and golden by frying or baking them however the bag says.
04 -
Toss mayo, ketchup, vinegar, relish, sugar, and chili flakes (if using) into a bowl. Mix until smooth. Set aside for later.
05 -
Heat up butter and oil in a pan on low-medium heat. Add your chopped onions and salt. Stir them now and then. Take your time—let them turn sweet and golden, which takes about 30 minutes. If things are getting too brown fast, turn down the burner.