In a big mixing bowl add butter and icing sugar. Beat them with an electric beater till smooth and creamy. (if using hand whisk, beat them for more time)
Add milk to it and beat them again till smooth.
Scrap the sides with a spatula and beat them again till smooth and fluffy.
Sift whole wheat flour, custard powder and baking powder.
Add the oats to the sifted ingredients. Mix them well.
Now add the dry ingredients to the butter mixture. Mix them first with a spoon and then gently mix them with hands.
Add the dessicated coconut to the dough and knead it gently till smooth.
Wrap the dough in a plastic cling wrap and put it in freeze for 20-30 minutes.
After 30 minutes, remove the dough from freeze, unwrap it and smoothen the dough a little. Divide the dough in four equal parts. Take one portion and roll it into 2mm thick circle . You can use a baking sheet or plastic sheet to roll the dough. Cut into desired shapes with cookie cutter. I have cut them into 1inch by 1 inch square approximately.
Arranged the cut cookies in baking tray lined with baking paper. Repeat the same procedure with other dough.
Bake the cookies in a preheated oven @ 180 C for 15 min.
Remove the cookies on wire rack to cool and serve or store.