In a stand mixer, on medium speed, beat butter until smooth only a minute or two. Add the sugars until just combined. Add the egg and egg yolks until they are just mixed in.
Add the flour and salt to the butter mixture and mix until everything is just incorporated. Pour onto cling film and cover with another piece of cling film. Shape into a disk and refrigerate for at least 3 hours or overnight.
Preheat the oven to 350°F or gas mark 4.
Remove the disk from the refrigerator and roll out to desired thickness no thicker than ¼" . By using cling film or parchment paper to roll out the dough you can reuse the scraps without changing the texture of the dough. Refrigerate or freeze for a few minutes to let the dough firm up. If the dough was refrigerated overnight allow to sit for about 5 minutes before rolling as it will be quite hard.
Cut out the cookies in the desired shape and place onto the lined baking sheet. Bake for 10 minutes. The cookies should remain pale in color or with just a hint of brown on the edges.
Allow to cool for a couple of minutes before transferring to a cooling rack. Repeat with the remainder of the dough.