Pre-heat your oven to 180 degrees celsius (fan-forced) and line 2 trays with baking paper.
Place 2 cups of the corn flakes into a large bowl and set aside until needed.
Insert the butterfly attachment into your Thermomix bowl and add the softened butter and caster sugar. Mix for 40 seconds, speed 2 or until the mixture is pale and creamy.
Add the eggs and vanilla extra and mix for 10 seconds, speed 3.
Remove the butterfly attachment and add the self raising flour, coconut and bicarb soda. Using the dough function, mix for 50 seconds or until the mixture comes together.
Add 1 cup (35g of corn flakes), sultanas and chocolate chips and use your spatula to combine in the biscuit dough.
Use a dessert spoon to scoop up the mixture and roll into a ball. Place the mixture into the bowl with the extra cornflakes and roll to cover.
Place the biscuits onto your baking trays and gently flatten with the palm of your hand. Repeat until all of the mixture has been used.
Place the baking trays into your preheated oven and cook for 15 minutes or until golden.
Allow the Cornflake biscuits to cool on the baking trays for 5 minutes before carefully transferring to a wire rack to cool completely.