Can you recount the story of Kaka Mahajani's friend and his visit to Shirdi?

Certainly. According to Chapter 35, a friend of Kaka Mahajani, who was a great devotee of the formless and averse to idol worship, agreed to visit Shirdi out of curiosity. He set two firm conditions for his visit: he would not bow his head to the saint, nor would he offer any Dakshina. However, upon arriving at the mosque, Sai Baba saw him and spoke in a voice that was a perfect imitation of the friend's deceased father. This deeply moving experience caused the friend to completely forget his resolve and bow at Baba's feet. Later, when Baba asked for Dakshina only from Kaka Mahajani and not from him, the friend felt restless, showing a complete change of heart from his initial skepticism.