Sift together the flour and soda bicarbonate into a large bowl. Rub four tablespoons of ghee into the flour mixture with your fingertips till it resembles breadcrumbs.
Add the beaten yogurt and knead into a soft dough. Cover the dough with a damp cloth and allow it to rest for forty-five minutes.
Divide the dough into twelve equal portions and shape into smooth balls. Take care not to overwork the dough. Make a slight dent in the centre of the ball with your thumb. Keep the balls covered.
Heat sufficient ghee in a non-stick kadai on medium heat. Gently slide in the prepared dough balls, two to three at a time, and deep-fry on low heat. If necessary, place a non-stick tawa below the kadai so that the ghee does not get too hot.
Gradually the balushahi will start floating to the top. Turn gently and fry the other side till golden. The entire process may take around half an hour to forty-five minutes. Remove with a slotted spoon and drain on absorbent paper. Set aside to cool for forty-five minutes, or till they reach room temperature.
Cook the sugar with one cup of water in a deep non-stick pan on high heat, stirring occasionally, till the sugar dissolves. Add the milk to the cooking syrup. Collect the scum which rises to the surface with a ladle and discard. Continue to cook till the syrup attains a two-string consistency.
Remove the syrup from heat and soak the cooled balushahi in it for two hours.
Gently remove the balushahi from the sugar syrup and place on a serving plate. Decorate with the pistachios. Set aside for two to three hours till the sugar syrup forms a thin white coating on the balushahi.