In a small bowl, stir together the flour, baking powder and cornflour.
In a separate bowl, add the vegan butter, sugars and the seeds from the vanilla pod (reserve the pod for the jar of vanilla salt later). Beat until light, pale and fluffy. Slowly beat in the aquafaba until smooth.
Add half of the flour mixture into the beaten butter mixture and combine. Next, fold in the the rest of the flour mixture until you have a dough. Fold in the chocolate chips and pistachio nibs, reserving some chocolate chips to sprinkle on top halfway through baking.
Use a medium-sized ice cream scoop or your hands to make the dough balls. Place them on the baking tray in rows leaving a small gap around each one. Cover with cling film and refrigerate for 24 hours. You could also place into a lined airtight container and freeze for up to 6 months.
To make the vanilla salt, gently mix together the sea salt flakes and vanilla bean seeds. Store in an airtight container along with the scraped vanilla pods used for the salt and cookies.
When you’re ready to bake, preheat the oven to 170˚C/350˚F. Line three large baking trays with baking parchment. If baking from frozen, add an additional 3 minutes on to the cooking time.
Place the cold cookie dough balls onto the lined trays with enough room in between each for spreading.
Bake for 5 minutes, remove from the oven and wearing oven gloves, firmly bang each tray on the worktop a few times to flatten the tops and encourage the cookies to spread. Sprinkle with a few flakes of vanilla salt and more chocolate chips if you like. Return the cookies to the oven and bake for a further 8 minutes (11 minutes if cooking from frozen), until lightly golden around the edges.
Remove the trays from the oven and allow to cool slightly before eating. They’ll firm up as they cool down.