Cut your onion in half and then into slices about 1/2 inch thick. Separate the slices into rings and set aside.
Add 4cm of cooking oil to a frying pan on medium-high heat.
In a medium-sized bowl, add approx. 40g of Crispy Batter Mix. Pour in 60ml of beer or soda water and whisk until smooth.
In a small bowl, add 1/4 cup plain flour. Take each onion ring and coat evenly in the flour.
Dunk flour-coated onion rings into the batter mixture before adding directly to the hot oil. Be sure not to overcrowd the pan when cooking.
Fry the onion rings for around 2 minutes each side, or until golden brown. Place onion rings onto a cooling rack set over paper towels to drain excess oil.
Serve in a bowl or add to burgers.