Line a large baking tray with baking parchment
Using an electric whisk, mix together the butter and sugar until fully combined, pale and fluffy
Gradually add the eggs and orange zest, whilst mixing on a medium speed. Leave to one side
Stir together the flour, cornmeal, baking powder and salt in a large bowl
Add to the the sugar/egg mixture, one tablespoon at a time whilst mixing on a slow speed. Stop the mixer as soon as the last tablespoon of flour has been added
Add the chocolate and stir through until evenly distributed. You should now have a dough mix
Split the dough into 2 even halves and lightly shape into long flat sausage shapes. Double wrap in cling film
Freeze for one hour - It will really stiffen up. Preheat the oven to 180C
Bake for 25 minutes
Remove from the oven and allow to cool for 20 minutes
Using a saw knife, slice the biscuits into 1.5cm thick slices. The end pieces can be used to nibble on
Place cut side down on the baking tray and bake for another 8 minutes
Turn over so the other cut side faces down and continue to bake for a further 7 minutes
Allow to cool on a wire rack