01 - Trim the root end just enough so each onion stands upright without falling apart, then peel. Make 4 to 6 vertical cuts from top to root, stopping about ¼-inch from the base to keep layers connected. Rotate and add additional cuts to form 8 to 12 petals, then gently separate them with your fingers.
02 - Combine all dry breading ingredients — flour, cornstarch, smoked paprika, garlic powder, onion powder, salt, black pepper, and cayenne — in a shallow bowl. In a second bowl, whisk together the eggs and whole milk until uniform.
03 - Dip each scored onion into the flour mixture, ensuring all surfaces and petals are well coated. Shake off excess flour, submerge in the egg-milk wash, then return to the flour mixture. Press gently to adhere the coating to every petal.
04 - Pour vegetable oil into a deep pot or fryer and bring to 350°F over medium-high heat. Use a thermometer to maintain consistent temperature throughout frying.
05 - Lower one or two onions into the oil cut side down. Fry for 2 to 3 minutes until golden, then flip and continue frying for another 2 to 3 minutes until crisp and cooked through. Adjust heat as needed to keep oil at 350°F.
06 - Lift the fried onions out with a slotted spoon and transfer to a paper towel–lined surface to drain. Sprinkle with additional salt while still hot if desired.
07 - Combine mayonnaise, ketchup, prepared horseradish, smoked paprika, garlic powder, lemon juice, and a pinch of salt in a bowl. Stir until fully incorporated and smooth.
08 - Arrange the hot mini bloomin onions on a serving plate alongside the dipping sauce. For variety, offer ranch dressing or spicy aioli as additional options.