Can you describe the miracle of the grapes that occurred with Boss Dharamsee in Shirdi?

Certainly. The story from Chapter 35 recounts how Kaka brought grapes with seeds as an offering to Sai Baba. When Baba began distributing them, he gave some to Boss Dharamsee, who disliked this variety and was also concerned they were unwashed. He ate the first ones reluctantly, pocketing the seeds. When he mentally challenged Baba's awareness of his dislike, Baba gave him more. Dharamsee held these in his fist until Baba commanded, 'Throw them in and eat.' Upon obeying, Dharamsee was astonished to find that the grapes, which he knew had seeds, were now completely seedless. This experience shattered his skepticism and established his faith in Sai Baba's divine power.