I read that Baba compared the sweetness of a prasad to a famous sweet from Delhi. Is that story in this chapter?

While Chapter 18 does mention sweetness, it is in a completely different context and has no connection to Delhi or any physical prasad. The text refers to the spiritual 'sweetness' of the divinely inspired book, the Uddhava Gita (also known as Nath Bhagawat), which was so profound it caused Tukaram to perform a thousand readings. This spiritual sweetness is the focus, not a comparison to any food from Delhi. The passages from Chapter 18 instead elaborate on Baba's practice of having these sacred books read daily for the benefit of his devotees.