Step-by-Step Instructions

1. 1.Prepare the Base Mixture

   In a mixing bowl, combine 125g of unsalted butter (at room temperature), 1/2 cup of caster sugar, and 1 teaspoon of vanilla extract. Cream the mixture together using an electric mixer until it is smooth. If you don't have an electric mixer, you can use a silicone spatula and smush it together by hand. Check for smoothness by rubbing a small pinch between your fingers; if it's gritty, continue beating.

2. 2.Add Flour to the Base

   Gradually add 1.5 cups of plain or all-purpose flour to the creamed butter mixture. Mix it in carefully until a soft, crumbly dough forms that holds its shape when pressed together.

3. 3.Prepare the Baking Pan

   Lightly grease a 20cm (8-inch) square cake pan. Line the pan with non-stick baking paper, ensuring that there are long handles on at least two sides to help lift the slice out later.

4. 4.Press the Base into the Pan

   Transfer the crumbly dough mixture into the prepared pan. Spread it out evenly and then use a flat-bottomed glass to firmly press the dough down until it is compact, smooth, and even all over the bottom of the pan.

5. 5.Bake the Base

   Place the pan with the base into a preheated oven at 180°C (360°F). Bake for approximately 12 to 15 minutes, or until the base achieves a very light golden color.

6. 6.Prepare the Caramel Layer

   While the base is cooling, start making the caramel. In a saucepan over a medium-low heat, combine a 400g can of sweetened condensed milk, 125g of butter, and 2 tablespoons of golden syrup. Stir the mixture gently and constantly for about 8 to 10 minutes. The butter will melt, and the mixture will slowly thicken and change from a pale creamy color to a beautiful light tan/bronze caramel color. Be extremely careful as you are working with super hot sugar.

7. 7.Pour Caramel Over the Base

   Once the caramel mixture has thickened and reached the desired color, switch off the heat. Carefully and quickly pour the hot caramel over the baked biscuit base in the pan. Gently smooth it out evenly over the base using a wooden spoon. Any butter/oil on top will absorb into the caramel layer when chilled.

8. 8.Bake the Caramel Layer

   Return the pan with the caramel layer to the preheated oven at 180°C (360°F) for about 10 minutes.

9. 9.Cool Completely

   Carefully remove the caramel slice from the oven. Place it on the counter and allow it to cool completely to room temperature. This step is crucial; the slice must be entirely cool before adding the chocolate topping to prevent the chocolate from splitting or melting improperly.

10. 10.Prepare the Chocolate Topping

    In a heatproof glass bowl, combine 250g of milk chocolate buttons and 1 tablespoon of plain vegetable oil. Lightly toss the chocolate and oil with a metal spoon. Melt the chocolate in the microwave in 30-second intervals, stirring with the metal spoon after each interval, until it is completely melted, smooth, and glossy.

11. 11.Add Chocolate Topping and Chill

    Pour the melted chocolate over the completely cooled caramel layer. Gently smooth it evenly over the entire surface. Place the pan into the fridge to chill for a few hours, or until the chocolate topping has fully set and is firm.

12. 12.Slice and Serve

    Once the slice is firm and the chocolate has set, gently lift it out of the pan using the baking paper handles. If desired, you can trim the edges for a perfect look. Heat a very sharp knife in hot water, dry it thoroughly, and carefully slice the caramel slice into squares. Wipe and reheat the knife after each cut to ensure clean, precise slices. Serve and enjoy your delicious homemade caramel slice!