Preheat oven to 200°C (390°F). Brush a 20cm fluted loose-bottomed round tart tin with butter and dust with sugar. Line the tin with the pastry and trim the excess. Prick the base with a fork. Line with non-stick baking paper, fill with baking weights or uncooked rice and blind bake for 15 minutes. Remove the baking paper and weights and bake for a further 10 minutes or until golden and crisp. Set aside to cool. Place the condensed milk, golden syrup and butter in a saucepan over low heat. Cook, stirring continuously, for 2–3 minutes or until thickened slightly. Pour into the pastry case and refrigerate for 30 minutes or until set. Place the chocolate and cream in a saucepan over low heat and cook, stirring, until melted and smooth. Spread the chocolate mixture over the caramel and refrigerate for a further 30 minutes or until set. Serves 6.