Step 1: Make the Caramel Sauce

1. In a small saucepan over low heat, melt the butter with golden syrup and salt.
2. Stir in the sweetened condensed milk and cook for about 5 minutes, stirring constantly, until thick and golden.
3. Remove from heat and set aside to keep warm.

Step 2: Prepare the Brownie Batter

1. Preheat your oven to 350°F (175°C). Line an 8-inch (20cm) square baking pan with parchment paper.
2. In a microwave-safe bowl, melt the butter and chocolate together in 30-second intervals, stirring in between, until smooth.
3. Whisk in both sugars, then add eggs and vanilla. Mix until well combined.
4. Sift in the flour, cocoa powder, and salt, folding gently until just incorporated.

Step 3: Assemble the Brownies

1. Pour two-thirds of the brownie batter into the prepared pan and spread evenly.
2. Drizzle the caramel sauce over the batter, leaving a little room at the edges.
3. Dollop the remaining brownie batter on top and use a knife to swirl the caramel into the batter.

Step 4: Bake & Cool

1. Bake for 30–35 minutes or until a toothpick inserted in the center comes out with moist crumbs.
2. Let the brownies cool completely in the pan before slicing. For clean cuts, refrigerate for 20 minutes before slicing.