01 - Peel each onion and trim just enough of the root so it stands upright. Make four evenly spaced vertical cuts downwards, keeping the base intact. Rotate and make four additional cuts between the first set. Gently separate petals with your fingers.
02 - Submerge cut onions in ice water for 10 minutes to encourage petals to open. Drain thoroughly and pat onions dry with paper towels.
03 - In a mixing bowl, combine flour, cornstarch, paprika, garlic powder, onion powder, cayenne pepper, salt, and black pepper. Whisk until evenly blended.
04 - In another bowl, beat eggs with whole milk until fully incorporated.
05 - Dredge each onion in the flour mixture, shaking off excess. Submerge in egg mixture, then coat in flour mixture again. Press petals to ensure even coverage.
06 - Bring vegetable oil to 350°F in a deep fryer or heavy-bottomed pot.
07 - Fry onions in batches, placing them cut side down for 2 to 3 minutes. Flip and continue frying for an additional 2 to 3 minutes, until deeply golden and crisp. Drain on paper towels.
08 - In a bowl, mix together mayonnaise, ketchup, horseradish, smoked paprika, garlic powder, salt, and black pepper until smooth.
09 - Serve mini bloomin' onions warm, accompanied by dipping sauce.