In a medium bowl, combine the ¾ cup mayonnaise, 1 tablespoon fresh lemon juice, 1 teaspoon crushed garlic, and 1½ tablespoons sriracha or hot sauce. Season with Kosher salt and freshly ground black pepper to taste. Mix well, cover, and refrigerate until ready to use.
Place each cube steak between sheets of plastic wrap. Use a meat mallet or rolling pin to pound the steaks until they're less than ¼-inch thick. Salt the steaks lightly with Kosher salt.
Preheat the oven to 200°F. Place a wire rack over a baking sheet in the oven to keep the cooked steaks warm.
In one shallow dish, whisk together 2 large eggs and 1 cup milk. In another dish, combine 2 cups all-purpose flour, 2 teaspoons kosher salt, 2 teaspoons ground black pepper, 1 teaspoon garlic powder, ¾ teaspoon smoked paprika, and ½ teaspoon cayenne pepper. Dredge each steak in the flour mixture, then dip it in the egg wash, and coat it again with the flour mixture. Set aside on a plate.
In a large frying pan, heat 1 cup canola oil to 350°F and add 1 tablespoon unsalted butter. Carefully lay a coated steak in the hot oil and fry for about 2 minutes on each side, until golden brown. Transfer the fried steak to the wire rack in the oven to keep warm.
Lightly toast the hamburger buns and spread a layer of spicy mayo on the bottom half of each bun.
Top each bun with a crispy chicken fried steak and a fresh lettuce leaf. Spread more spicy mayo on the inside of the top bun and gently close the sandwich.