Preheat the oven to 180C/350F and spray an 8 inch skillet with cooking spray. If you are making individual cookies, don't preheat the oven yet as the dough needs to chill.
Place the butter and sugar into a large bowl, or the bowl of your stand mixer, and beat until light and fluffy. Around 2 minutes on medium-high speed.
Scrape down the sides as necessary, then add in the golden syrup and vanilla and mix until well incorporated.
Place the flour, cornflour, baking powder, bicarbonate of soda, salt and chocolate chips into a medium sized bowl and stir briefly to coat the chocolate chips in flour.
Tip the flour mixture into your butter mixture, add in the milk and then mix on medium speed until your dough comes together. You want no lumps of flour, the dough will be a little sticky and ball up into one large lump.
If you are making a skillet cookie: Tip the cookie dough into your prepared skillet and smooth into an even layer. Place in the oven for 18 minutes at 180C/350F and then turn down the oven to 160C/325F for another 7-8 minutes. The cookie should be risen, golden all over and when you insert a skewer into the centre a few crumbs should come out. This cookie is best if slightly underbaked in the centre. Leave to cool for at least 30 minutes, before adding ice cream of your choice, grabbing a spoon and digging in.
If you're making cookies (this dough will make around 10 cookies): Place the dough back in the bowl you measured the flour into and cover with cling film. Place in the fridge for 2 hours to chill. Once chilled, line a tray with grease proof paper/a silicone mat. Use a 1.5tbsp cookie scoop to place rounds of cookie dough 2 inches apart on the tray. Flatten the dough balls ever so slightly with your palm, then place in the oven for 9-11 minutes. They should be golden all over, slightly crisp around the edges and soft in the middle. In the oven light, they will look matte on top.
Leave the cookies to cool completely on the tray. Egg Free Chocolate Chip Cookies will keep in an airtight container, at room temperature, for 5 days. The skillet cookie will keep in an airtight container for 5 days also. I would advise, if you don't eat the entire skillet cookie on the first day, you transfer it from the skillet to an airtight container because it will start to taste metallic if you leave it overnight.