Crust

• Prepare: Preheat your oven to 175°C (350°F). Lightly grease the base and sides of a square 8" pan or rectangular 9" pan with some oil or vegan butter, then line it with parchment paper.
• Make the crust: In your food processor, combine all of the crust ingredients until they stick together to form a dough. Evenly press the dough into the base of the pan.

  Place a sheet of parchment paper on top of the crust and compact it down by smoothing it out with a flat-bottomed glass. Peel off the parchment, and use a fork to prick the dough several times.
• Bake: Bake for 14-15 minutes until slightly browned, then allow it to cool to room temperature. If using plain flour, the bake time will be 15-18 minutes.
• Make the caramel: Add the condensed milk, white and brown sugar, and butter to a saucepan and melt over medium heat. Continue to heat whilst stirring.

  Place your candy thermometer in the caramel and heat until it reaches 120°C (248°F).

  Remove from the heat and stir in the sea salt and vanilla if using. Allow the caramel to cool slightly for 5 minutes.
• Assemble: Pour the caramel over the shortbread base and allow it to reach room temperature before transferring it to the fridge for at least 3 hours (or overnight).
• Make the coating: Melt the chocolate and butter over a double boiler. Stir until melted thoroughly. Use a spatula to spread it over the caramel in an even layer. Sprinkle sea salt on top.
• Serving: Allow the slice to set at room temperature for at least 15 minutes before slicing it into servings.

  Cut slowly, applying pressure to the chocolate until you can see that the knife has made its way through it, then press down to cut through the caramel and biscuit layers. 
• Storage: Place in an air-tight container and refrigerate for up to a week.

  Alternatively, you can freeze them in a sealed container and defrost them for an hour or two before serving.