Ashima is craving something spicy.  Part of this craving might come from her being pregnant.  Yet, another part of it might come from the fact that she has left an intense culture and moved into a relatively tepid one.  Her placement in the cold and frigid Northeast is a far departure from the heat and humidity of Bengal, India.  It is for this reason that she reaches for dry cereal, peanuts, and any semblance of spice that she can find.  It is to satisfy a craving.  This craving is partly biological, due to her pregnancy.  Yet, it also cultural.  The world in which she lives is one where there is a noticeable absence of intensity and spice.  In mixing "Rice Krispies with Planters peanuts, chopped red onion, salt, lemon juice and green chili peppers," Ashima wishes to recreate something that reminds her of home in a world.  This recreation takes on the sensual and psychological dimensions.  It is for this reason that her craving in the exposition of the novel is significant.  It shows her striving to straddle both worlds.  It also shows her in a divided state of consciousness, one that won't be fully resolved until the end of the novel.