Mix together all dried ingredients in a large bowl.
In a separate large bowl, mix together eggs and milk.
Remove the papery skin, and then cut off ½ inch from the pointy end of the onion.
Place the onion cut-side down on a cutting board and start ½ inch from the root, cut vertically downward.
Repeat and you will get about 12-16 sections.
Turn the onion over and it will look like an onion flower. Open the onion petals more with your fingers.
Place the onion flower in the flour mixture. Lift and shake off excess flour.
Place into the egg wash, and return to the flour mixture.
Lift the onion and place onto a plate. Freeze for 30-60 minutes.
In a deep fryer or pot, heat the oil to 350°F.
Place the onion flower into the pot, cut-side facing down. Fry for 3-4 minutes. Turn it over and fry for another 3-4 minutes until golden brown.
Transfer to a plate lined with paper towel.
Mix the thousand island and creamy horseradish sauce to make the blooming onion sauce.
Dip the bloomin onion petals into the dipping sauce and enjoy!