In a bowl whisk together whole wheat flour, baking soda, baking powder, and cardamom powder. Keep aside. Add butter and brown sugar and whishk it till fluffy and smooth. Now add dry ingredients into it and mix it well.

Add cold milk to the mixture.
Knead lightly to form a dough. Do not over knead.
Dust some flour on the countertop.Using a rolling pin roll out the dough to 1/4 inch thickness. Using a cookie cutter cut out the cookies in square shape.Roll again the remaining dough and cut out the square shape cookies. Arrange the biscuits on a prepared baking tray.
Bake them in a preheated oven at 160°C for 20-25 minutes or till they are light brown in color.
Let them cool on a wire rack.

Now we gonna make Royal Icing. For that add icing sugar in a bowl then add all ingredients of Royal Icing section one by one and mix it calmly. If you feel your icing is more thick add little more corn syrup in it and mix it well. Make sure that it's not too runny.