In a medium bowl, cream together the butter, chocolate topping, brown sugar and white sugar until smooth. Beat in the eggs, one at a time, then stir in the golden syrup and vanilla. Combine the flour, bicarb soda and salt; stir into the creamed mixture until just blended. Mix in the chocolate bits by hand. Drop biscuits by 1/4 cupfuls onto ungreased baking trays.
Bake for 12 to 14 minutes in the preheated oven. Allow biscuits to cool on baking tray for 5 minutes before removing to a wire rack to cool completely.