Preheat your oven to 160°C (320°F). Line a square baking pan with parchment paper, leaving some overhang for easy removal.
In a mixing bowl, combine the flour, sugar, and a pinch of salt, then stir until evenly mixed.
Add the cold, cubed butter to the dry mixture. Rub in with your fingers or a pastry cutter until the mixture resembles coarse crumbs, and starts to clump together.
Press this buttery crumb mixture firmly into the prepared pan, spreading it out evenly with your hands or a spatula. Bake for 20-25 minutes until golden around the edges and fragrant with toasted butter aroma.
While the base cools slightly, pour the golden syrup into a saucepan over medium heat. Add the sweetened condensed milk and melted butter (if cooled slightly), stirring constantly.
Cook the mixture, stirring continuously, until it thickens and turns a deep amber color, about 8-10 minutes. It will bubble and smell sweet and caramelized.
Once the shortbread base is baked and slightly cooled, pour the hot caramel evenly over it. Use a spatula to spread it out smoothly.
Return the pan to the oven and bake for an additional 10 minutes until the caramel is bubbling around the edges, filling the kitchen with a warm, sweet aroma.
Remove the pan from the oven and let it cool at room temperature for about 30 minutes. Then, transfer it to the fridge and chill for at least 2 hours until the caramel is firm and set.
Meanwhile, melt the dark chocolate in a microwave or double boiler until smooth. Drizzle it over the cooled caramel layer in a zigzag pattern for a decorative touch.
Once the chocolate is set, use a sharp knife to slice the caramel shortbread into squares. Serve chilled or at room temperature, enjoying the crunchy base with the gooey caramel and chocolate topping.
