Thoroughly pat your wings dry with paper towels (see blog post/video for guidance on dividing whole wings) then place in a zip lock bag. Add 2 tsp baking powder (not baking soda/bicarb soda!), 1/2 tsp salt and mix about with your hands until fully coated.
On an oiled wire rack above a tray lined with foiled, space out your wings skin side up. Bake at 250F/120C on the lower-middle rack for 30mins. This step is to render down the fat, not to cook them through.
Take them out, turn the tray around, then place in the middle-higher rack at 430F/220C until golden and crispy. This will take approximately 40-45mins, with larger wings taking up to around 50mins and smaller ones potentially slightly less. Take out the tray half way and rotate again. All ovens can be slightly different, so just be vigilant. If they start to char at all turn down the heat and lower the rack.
Meanwhile, in a small pot over medium heat add brown sugar, apple cider vinegar, ketchup, pineapple juice and give it a stir until fully blended. In a small cup, combine 1 tbsp soy sauce with 1 tbsp cornstarch/cornflour until completely blended (make sure there's no lumps). Pour this into the sauce and quickly stir to combine. Simmer for a few mins until the sauce thickens, then take off heat. *taste test for sweetness/acidity and adjust to your liking with more sugar or vinegar.
Once the wings are cooked allow them to rest for a few mins, then combine in a large bowl with the sauce.
Serve by sprinkling over sesame seeds and finely diced spring onion.