Can you tell me the story of how Sai Baba knew that Laxmichand wanted to eat khaja?

Certainly. The story of Laxmichand and the khaja is a wonderful example of Sai Baba's omniscience. As told in Chapter 28, during a visit to Shirdi, Laxmichand developed a craving for a sweet called khaja after having a small piece. This desire lingered in his mind for a couple of days. On the third day, when devotees were asking Baba what food offering (naivedya) they should bring, Baba specifically requested a plate full of khaja. Later, Baba commented on the 'wind of khaja' blowing and ensured it was served, perfectly fulfilling Laxmichand's unexpressed wish and satisfying his hunger, which left Laxmichand full of joy.