In a large bowl put the flour, bicarbonate of soda and cornflour in a large bowl. Set aside.
In a medium size bowl, whisk the melted butter and both sugars together until no brown sugar lumps remain. Whisk in the egg, then the egg yolk. Finally, whisk in the vanilla.
Next add your dry ingredients and mix together with a large spoon. The dough will be very soft and thick. Fold in the butterscotch chips and honey roasted peanuts, saving some to place on top for decoration. They may not stick to the dough because of the melted butter, but try to have them evenly dispersed among the dough.
Cover the dough in clingfilm and chill in the fridge for at least 2 hours or if you like overnight. You must not skip this step otherwise you will end up with big splodges!
Take the dough out of the fridge and allow to slightly soften at room temperature for 10 minutes.
Preheat the oven to 180C degrees. Line two large baking trays with parchment/baking paper. Set aside.
Roll the dough into balls, about 3 Tablespoons for each cookie. Roll the cookie dough into balls and do not flatten them. This will keep the cookies nice and thick.
Press a few more butterscotch chips and peanuts on top of the dough balls if desired. Bake the cookies for 10-12 minutes. The cookies will look very pale but this is what you want for that chewy texture. Allow to cool on the cookie sheet for 10 minutes before moving to a wire rack to cool completely.