01 - Separate the onion slices into individual rings and set aside.
02 - In a large bowl, whisk together flour, cornstarch, baking powder, salt, black pepper, and smoked paprika until evenly mixed.
03 - In a separate bowl, whisk the eggs and cold sparkling water until thoroughly combined.
04 - Gradually add the wet mixture to the dry ingredients, whisking continuously until a smooth batter forms.
05 - Place panko breadcrumbs in a shallow dish for breading.
06 - Heat vegetable oil in a deep fryer or heavy pot to 350°F (175°C).
07 - Dip each onion ring into the batter, allowing excess to drip off, then thoroughly coat with panko breadcrumbs.
08 - Carefully lower the coated rings into the hot oil in batches, frying for 2 to 3 minutes or until golden brown and crisp.
09 - Remove the fried onion rings using a slotted spoon and drain on paper towels.
10 - Serve the onion rings hot accompanied by your preferred dipping sauce.