• Grease a 9 x 13-inch (23 x 33cm) baking pan and line with parchment paper bringing the paper up over the two long side to make it easy to remove. Preheat the oven to 350°F (180°C).

To make the base:

• Combine all ingredients in a large bowl. Press the mixture over the bottom of the pan using a flat-bottomed glass. Bake for 15 minutes or until golden brown around the edges.

To make the filling:

• Stir all the ingredients together in a medium saucepan over medium-low heat until the butter is melted. Then stir constantly for 8 minutes or until the mixture is slightly thickened (be careful as this mixture can burn easily). Pour the filling over the hot base and spread until smooth. Bake for 10 minutes or until bubbling and lightly browned around the edges; cool.

To make the topping:

• Stir the chocolate and butter together in a small saucepan over medium low heat for 5 minutes or until the chocolate is almost melted. Remove from the heat and continue to stir until the chocolate and butter are melted. Spread the warm topping over the cooled filling. Let stand at room temperature until cool. Cover and refrigerate for about 4 hours or until cold.
• Using the paper, carefully lift from the pan. Cut into 32 squares to serve.