Preheat oven to 180°C / 160°C fan. Line an 8x8-inch tray.
Cream butter, sugar, and vanilla together.
Mix in flour and cornflour to make a crumbly dough.
Stir in the chocolate.
Press dough into the tray and score where you’ll cut later.
Sprinkle with sugar and bake for about 45 mins.
Rescore while warm, cool in the tray, then cut into bars. Enjoy!
