Instructions:
- Prepare the Onions: Slice onions pole-to-pole (root to tip) as thinly as possible (ideally 1/16 inch or 1.5mm). If using a mandoline, be careful!
- Rinse and Rest: Place sliced onions in a large bowl, cover with cold water, and gently swirl. Drain immediately, then spread them out on several layers of paper towels. Pat them very dry. Let them air dry for an additional 15 minutes.
- Create the Coating Mix: In a medium bowl, whisk together the flour, cornstarch, 1 teaspoon salt, pepper, and smoked paprika until thoroughly combined.
- Coat the Onions: Toss the dried onion slices into the flour mixture until lightly and evenly coated. Shake off any excess flour; they should look dusted, not crusted.
- Heat the Oil: Pour the oil into a large, heavy-bottomed skillet to a depth of 1.5 inches. Heat slowly over medium-high heat until the thermometer reads 350°F (175°C).
- Fry in Batches: Carefully drop about 1 cup of onions into the hot oil. Do not overcrowd the pan. Fry for 2–3 minutes, gently stirring occasionally with a slotted spoon to separate them.
- Achieve Golden Perfection: Continue frying until the onions turn a deep, rich golden brown. Use a kitchen thermometer to monitor the oil temperature closely.
- Drain Immediately: Use the spider strainer to quickly lift the onions out of the oil. Transfer them immediately to a wire cooling rack set over a baking sheet lined with paper towels.
- Final Seasoning: While still piping hot, immediately sprinkle generously with extra fine sea salt.
- Repeat and Cool: Repeat the frying process with the remaining batches, ensuring the oil returns to 350°F (175°C) between batches. Allow them to cool completely before serving or storing to maximize crispness.