plain flour, 40g cornflour, salt and pepper, cold fizzy water. Mix the dry ingredients and slowly add enough water to a thin consistency that will stay on the back of a spoon. Dip raw onion rings into the batter and then into hot oil. You could use a small saucepan with enough oil to submerge the onion rings. Heat to around 170ºC - drop a little batter into the oil and if it rises to the surface and bubbles, that's about the right temperature.
yes cheese, potato & lots of onions in a crisp shortcrust pastry case. Cheese & onion pie in my area of the UK is usually made with a tasty Lancashire, it's also amazing made with Wensleydale or Caerphilly or any other crumbly type
Alternatively, dip thin slices of uncooked potatoes, spinach, kale or thinly sliced aubergine in the batter and fry until golden and the vegetables cooked through – this would be the Asian alternative to Japanese tempuras, but spicier