In a bowl, mix together the dry ingredients – flour, baking powder, salt and milk powder. In another bowl, add the melted butter and sugar and mix well. Also add the water and vanilla extract to the butter sugar mixture and stir in to mix well. Add the wet ingredients mixture slowly to the dry flour mixture to get a crumbly mixture. Make sure its mixed well so all the ingredients are evenly combined. Knead well with hands to form the cookie dough.