Heat the oil in a Dutch oven or deep fryer to 375 degrees F.
Wash the okra, drain thoroughly and pat dry. Cut off the ends of the okra, and then cut the okra crosswise into 1/2-inch rounds.
In a medium bowl, combine the flours, baking powder, 1 teaspoon salt, baking soda, 1/2 teaspoon cayenne and 1/4 teaspoon white pepper. In a small bowl, combine the remaining 1/2 teaspoon salt, 1/2 teaspoon cayenne and 1/4 teaspoon white pepper and set aside.
Place the cornstarch in a small bowl.
When the oil is hot, add the hot sauce and ice water to the spiced flour. Gently mix; there will be some small lumps.
Skewer the okra pieces through the middle of the flesh, leaving enough room between each piece of okra so they can fry individually. Repeat with remaining okra. Dredge the skewers through the cornstarch. Place into the tempura batter and then immediately and carefully into the hot oil.
Fry the okra in batches until browned, 4 to 6 minutes for each batch. Drain on paper towels, sprinkle with the reserved salt and spice mixture and serve immediately with Spicy Ranch Dressing.
Spicy Ranch Dressing:
Mince the garlic and then add 1/2 teaspoon kosher salt and mash with the edge of the knife until a paste is formed.
Add this to a blender with the remaining ingredients. Puree and taste to adjust seasoning.
Remove and place in a small bowl and refrigerate for 1 hour.