Stir together butter and sugar with a spatula in a big mixing bowl until its well mixed.
Add vanilla essence, egg, and oil. Mix vigorously until smooth.
Sift all the purpose flour, corn flour, baking powder, bicarbonate of soda, and salt into the mixing bowl. Stir until combined.
Tip in chocolate chips and chopped pecaks into the bowl and fold until just mixed.
Chill in the fridge for at least 30 mins.
10 minutes before you take out your cookie dough, heat the oven at 150°C on fan. Ball your dough into 1 inch golf balls and arrange on pans lined with baking sheets.
Bake for 15 minutes. The cookies are done when they are firmly set, lightly browned and leaves no imprint when you touch them with your finger.
Keep cookies fresh in an airtight container.