01 - Peel onions and trim bases so they stand upright. Using a sharp knife, make 4 vertical cuts down each onion without cutting through the base, then rotate and make 4 more cuts between the previous ones. Carefully pull apart petals to open the 'bloom.'
02 - Place cut onions in ice water for 10 minutes to encourage petals to open. Drain thoroughly and pat dry using paper towels.
03 - In a mixing bowl, combine flour, cornstarch, paprika, garlic powder, onion powder, cayenne, salt, and black pepper. In a separate bowl, whisk together eggs and milk until fully blended.
04 - Coat each onion in the flour mixture, shaking off any excess. Dip into egg mixture, then dredge again in the flour mixture, pressing petals gently to ensure an even coating.
05 - Heat vegetable oil in a deep fryer or heavy-bottomed pot to 350°F. Working in batches, fry onions cut side down for 2–3 minutes. Carefully flip and continue frying another 2–3 minutes until golden brown and crisp. Remove with a slotted spoon and drain on paper towels.
06 - In a mixing bowl, blend mayonnaise, ketchup, horseradish, smoked paprika, garlic powder, salt, and black pepper until smooth and well combined.
07 - Present mini bloomin' onions warm alongside the dipping sauce.