In a blender, combine mayonnaise and kimchi. Set aside to serve later. Combine two teaspoons salt, a quarter-cup cornflour, and half the baking powder in a large bowl and mix until combined. Add chicken wings and toss until every surface is coated. Place wings on a wire rack and refrigerate, uncovered, overnight. When ready to fry, preheat oil to 180C in a deep-fryer. Combine remaining cornflour, baking powder, two teaspoons of salt and flour in a large bowl and whisk until combined. Add water and whisk to a smooth batter. Working one at a time, lift one wing into the batter and allow excess batter to drip off, using your finger to get rid of any large pockets of batter. Carefully lower wing into hot oil. Repeat with remaining. Using a metal spider or slotted spatula, rotate and agitate wings as they cook, until evenly golden brown and crisp all over (about 8 minutes). Transfer to a paper towel-lined plate and season immediately with salt. Keep warm while you fry the remaining wings, then serve with kimchi mayonnaise.