Preheat oven to 180 degrees celsius (fan-forced). Grease and line two flat trays with baking paper and set aside.
Cream butter, sugar and vanilla extract on Speed 4, 30 seconds. Scrape and repeat 2 more times or until pale and creamy.
Add the self raising flour and milk and mix on Interval (kneading function) for 20 seconds. Scrape down the sides and repeat.
Add the sultanas, chocolate chips and cornflakes and mix on Reverse, Speed 3, 5 seconds (use the spatula to help mix).
Scoop up tablespoonfuls of the mixture and roll into balls.
Press into the extra cornflakes to coat.
Place onto the prepared trays and press down to flatten slightly (allow space between each cookie as they will spread).
Bake for 13 minutes or until golden (check halfway and turn the trays around).
Allow to cool for 10 minutes on the baking trays before transferring to a wire rack to cool completely.
Store in an airtight container at room temperature for up to 1 week.