In a bowl add butter and whisk it for a while until it gets light in colour. I have used electric beater, you can even use hand whisker. Then add powdered sugar in it & whisk it in medium to high speed until it gets light & fluffy.

Then add vanilla essence, egg yolk and again whisk it. Now add all the dry ingredients by putting a strainer over the vessel, as shown in the image below.

Combine all the dry ingredients, including flour, cournflour & cocoa powder. Give everything a good mix. Now put the mixture into a piping bag.

Now for pre-heating, take a kadai with it's base covered with salt and a stand over it. Cover it and pre-heat the kadai for 5 mins on high flame and then 3 mins. on medium flame.

Now grease a plate with some oil and give the desired design of your choice, for cookies. Keep it in refrigerator for about 20 mins. Then remove it and put some choco-chips, as design over it, as shown below and place it over the stand, in the kadai.

Now cover it and bake it on a low flame for about 15 mins. Now remove the tray from the kadai. Let it cool down completely & then serve it. Repeat the same with the rest of the batches.