Heat oven to 180°C/350°F/160°FF
Line baking trays with baking paper.
Sift the flour, bi carb soda, baking powder and salt together. Set aside
In the bowl of a stand mixer, combine the butter and sugars until well blended
Add the egg, egg yolk and vanilla and beat until light and creamy (beating on medium-high for 5 minutes)
Stop the mixer, add the flour mixture and beat until almost combined
Remove bowl from stand, add chopped chocolate and popcorn, then combine with a wooden spoon or spatula. DO NOT OVERMIX
Using a large ice-cream scoop, scoop out heaped balls of cookie dough onto prepared baking sheet, leaving plenty of space to spread.
Press extra popcorn into the top of each dough ball, then press the dough down slightly
Bake for 12 minutes, until lightly golden, then remove from oven and scoot cookies back into shape with a large round cookie cutter, if desired
Let cool on tray for 5 minutes, before cooling completely on a cake rack