Preheat your oven to 190ºC/170ºC fan, and line a 9x9inch square tin with parchment paper, and leave to the side for now.
Melt the unsalted butter, and add to a bowl.
Add in the dark brown soft sugar and whisk the mixture together for two minutes.
Add in the egg and vanilla extract and whisk again until combined.
Add the plain flour, bicarbonate of soda, sea salt, cornflour, ground ginger, ground cinnamon and ground nutmeg together to the bowl.
Mix together until a thick cookie dough is combined.
Add in the white chocolate chips and mix.
Push half of the mixture into the 9x9inch tin - I find it easier to use a lightly floured spatula to spread this evenly.
Spread the caramel over the base cookie, leaving a small gap around the edge with no caramel. If you want it salty, sprinkle over the extra sea salt chunks now.
Add the second half of the cookie dough to the tin - I find it easier to place it on in small lumps until its covered the caramel - as pushing it around the tin will ruin the caramel.
Bake the caramel gingerbread cookie bars in the oven for 18-22 minutes. I usually do 19 minutes so they stay reasonably gooey.
Once baked, leave in the tin to cool, and then enjoy!