Put butter, coconut oil, vanilla, salt, baking soda and sugar in a mixing bowl and mix on medium for 5 minutes.
Add the egg, and once fully combined, add the flour.
Knead the dough on a floured surface for a few minutes. It will feel almost like a little cloud but shouldn't be sticky!
Divide the dough in half and wrap each half in clingfilm. Chill it in the fridge for 30 minutes.
Preheat oven at 350°F/175°C. Line two baking trays with parchment paper. Roll out dough on a floured surface until dough is ¼ inch thick. Using a 4cm/1.5inch round cookie cutter, cut out the cookies. Use a pastry tip to cut out the middle. Reroll the dough and continue cutting out your cookies, placing them on the tray when ready.
Bake in oven for 12 minutes.
Coconut Caramel
Preheat oven to 350°F/175°C. Line a baking tray with parchment paper and spread out the coconut on the tray. Toast for 8-10 minutes, checking after 4 minutes and shaking the pan so it gets evenly toasted. Let cool.
Line a loaf pan with parchment paper, set aside.
Put sugar, water and salt in a large saucepan and place over medium heat. Let it cook for 5 minutes, stirring occasionally. The sugar will dissolve and bubbles will appear around the edges of the pan.
Simmer until the syrup turns gold, do not stir. This takes about 8-12 more minutes. Once it turns gold, swirl the pan and let it cook for another 1-2 minutes. It should turn a deep amber.
Immediately add the cold cream and reduce the heat to low. Stir using a heat-proof spatula, then add in 1 tablespoon of coconut oil. Put your thermometer into the saucepan and continue cooking until it reaches 250°F/121°C. Fold in the toasted coconut.
Pour the caramel and coconut mixture into the loaf pan, and let it cool slightly.
Assembly
Once the caramel has cooled a bit, take one shortbread cookie and using a small offset spatula, scrape the caramel on to the cookie. I found it easier to get it to stick by first dipping the cookie into the caramel so it gets a bit sticky, then pile on more of the caramel.
After each cookie is coated, put it on a parchment lined baking sheet and put in the fridge to chill. Let the cookies chill for 30 minutes.
In a double boiler, melt 300 grams of dark chocolate. Once chocolate is completely melted, take your bowl out and set to the side.
Take your baking tray out of the fridge. Dip the bottom of each cookie into the melted chocolate, then place back on the tray to dry. I tried using a fork and a fondue stick to carefully dip the cookies in, but in the end I found it easier (though messy!) to just dip it in using my hands.
Once all the cookies have been dipped, fill a piping bag with the rest of the melted chocolate and drizzle on top. Or, you can always just dip a fork into the chocolate and drizzle! Let chocolate set.