In a medium size bowl, combine all the sauce ingredients (mayonnaise, sriracha, apple cider vinegar, Worcestershire sauce, garlic powder, sugar) then season with salt and pepper to taste. Set aside until ready to use.
Slice the top off the onion (opposite of the root) and peel. Flip the onion over on the cut side. Slice 1/2 inch from the root and 1/4 inch slices all the way around the onion, ensuring to keep the root intact. Flip the onion over and its petals should fan out or "bloom."
In a large bowl, combine the flour, corn starch, baking powder, smoked paprika, garlic powder, chili powder, salt, and pepper. Dredge the blooming onion in this seasoned flour mixture, making sure to get in-between all the petals.
In a separate large bowl, whisk and combine the milk, buttermilk, pickle juice, eggs, and a little salt and pepper. Take the blooming onion (which has already been dredged in flour) and fully immerse it in the milk and egg mixture, then immediately return it to the seasoned flour, ensuring all onion petals are thoroughly coated with both wet mixture and seasoned flour.
In a deep fryer, fill no more than 1/2 way with vegetable oil and heat to 375 degrees Fahrenheit. Safely lower the onion into the hot oil using a spider. Deep fry for about 5-7 minutes or until it is nice and golden brown. Remove the onion and drain on a wire rack, then immediately season with salt.
(Warning: Make sure the oil is not filled too high in the deep fryer. When you lower the onion into the hot oil, it will rise and risk spilling over the pot potentially causing a grease fire if not careful).
Serve the crispy blooming onion with the spicy dipping sauce on the side and optionally garnish with chopped parsley. Enjoy!
