01 - Peel onions and slice into rings approximately 1/2 inch thick; separate rings carefully and set aside.
02 - In a large bowl, whisk together flour, cornstarch, baking powder, salt, black pepper, and paprika until combined.
03 - Slowly whisk in cold sparkling water until the batter achieves a smooth and thick consistency.
04 - Spread panko breadcrumbs evenly on a shallow plate for breading.
05 - Heat vegetable oil in a deep pot or fryer to a steady 350°F (175°C) to ensure proper frying temperature.
06 - Dip each onion ring into the batter, allowing excess to drip off, then thoroughly coat with panko breadcrumbs.
07 - Carefully lower coated rings into hot oil in batches and fry for 2 to 3 minutes, turning once until golden brown and crisp.
08 - Remove fried onion rings with a slotted spoon and drain on paper towel-lined plate to absorb excess oil.
09 - Serve onion rings hot accompanied by your preferred dipping sauce.