In a mixing bowl add butter and add powdered sugar little by little and mix well.when the mixture become creamy texture add salt again mix it.then add 1cup wheat flour,besan flour,rava,baking soda knead it well.then add 1 tspn vanilla essence.then add milk little by little and knead it well.divide the dough in to two equal parts.one portion add 1 tbspn cocoa powder and 1 tbspn milk then knead it well.another dough is plain.