Add butter and sugar to mixer. Mix for about 5 min or till fluffy and whitish.
Add in egg yolk and vanilla essence and mix well.

Sift flour. Add 1/2 of the flour to mixture and fold.
Add the remaining flour and fold well.
Crush cornflakes to smaller pieces and mix well with the mixture.

Take a small dollop and make into a ball shape.
Preheat oven at 170 degrees celsius and bake for about 10-15 mins.
Take out from oven and let it cool for about 10mins.