Sieve the flour, baking soda, salt and cornstarch together, then mix into the batter until there are no lumps
Add ½ a cup each of white chocolate chunks, chopped pecans and butterscotch chips and mix through the dough so they are evenly incorporated
Cover and chill for 30 minutes
Preheat oven to 350°F / 180°C and line a large cookie sheet with parchment paper
Roll chunks of cookie dough into balls about the size of a golf ball and place on the cookie sheet, spread out with two inches between them
Use the palm of your hand to flatten each ball slightly
Bake for 10-12 minutes or until they just start to turn slightly golden brown a the edges. They will still be soft and doughy when they come out, but will harden slightly as they cool
Remove from the oven and sprinkle with a little bit of sea salt. Leave the cookies on the cookie sheet for at least 10 minutes before attempting to move them